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volunteer
Let's use the denominators for both fractions
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student
ok
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volunteer
So the denominator for fraction 1 is 1+x^2
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student
yes
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volunteer
Since x^2 is greater than or equal to 0, 1+x^2 is greater than 0
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student
yeah
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volunteer
Now for fraction 2, the denominator is x^3-x. We need to check to see if this expression is zero or not
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student
yep
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volunteer
So we set this expression equal to zero
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student
yep
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volunteer
So when we solve for 0, we get x=1, x=-1, and x=0
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volunteer
Therefore, the domain is {-1,0,1}
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student
ok
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student
why cant we sex x^2+1=0
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volunteer
We don't set x^2+1 to zero because it has no real solution
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student
how come?
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volunteer
Because when you do set this equal to zero you get x^2=-1
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volunteer
The square of any real number is always positive but -1 is negative
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student
what if when we multipled we got x^2=1
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volunteer
Multiplied when?
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student
what if isntead of x^2+1
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student
we had x^2-1=0
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volunteer
But that isn't the denominator in the first fraction of this problem
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student
what if it was
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volunteer
x^2+1=0 has no real solutions because x^2+1 is always greater than zero
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student
what if x^2-1
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student
does it have a solution
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volunteer
x^2 is greater than or equal to zero, therefore 1+x^2 is greater than zero
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volunteer
It has no restrictions
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student
yeah
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student
so whats domain
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student
of x^2-1=0
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volunteer
The domain of x^2-1=0 is all real numbers
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volunteer
Equations don't have a domain
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student
im saying if in denominatoe
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student
denominator
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volunteer
We don't look at individual equations and find the domains of them
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volunteer
Rather, we tried to find any restrictions for both equations and create a domain from that.
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student
yes what if x^2-1=0 so know in future
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student
how to solve
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volunteer
I'm confused on what your asking. Are you asking to solve for its solutions?
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student
i wanna know if was our domain]
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student
what domain would be
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volunteer
The domain is -1,0,1
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student
no '
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volunteer
Okay, let me rephrase. When you have a fraction, look for where the denominator equals zero
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student
cause x^2-1=0
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volunteer
The domain of x^2-1=0 is all real numbers. All polynomials (like x^2) can be defined on a number line, therefore making it all real numbers
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student
you cant do all real numbers
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volunteer
I'm confused what do you mean you can't do all real numbers?
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student
Step 1: Set denominator equal to zero and solve: 𝑥 2 − 1 = 0 x 2 −1=0 𝑥 2 = 1 x 2 =1 𝑥 = ± 1 x=±1 Step 2: Exclude these from the domain. Domain: All real numbers except 𝑥 = 1 x=1 and 𝑥 = − 1 x=−1.'
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volunteer
1 and -1 are just solutions, they aren't excluded from the domain
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student
they are the restrictions
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student
fpor x
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student
for
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volunteer
So restrictions occur when you have denominators or square roots of negative numbers
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volunteer
x^2 is a polynomial, and they work everywhere on a real line.
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student
im saying if a denomnator
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student
if x^2+1=-0
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student
in a random denom
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volunteer
There is no negative zero
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student
yes ik
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student
x^2+1=0
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volunteer
You don't set it equal to zero
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student
yes you do
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student
to find domain
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volunteer
Yes, you're right! Sorry, I'm getting confused here. But there are no real solutions
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volunteer
Because you can't have x^2=-1
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volunteer
Therefore the domain is still all real numbers
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student
what about x^2=1
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student
can you have that?
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volunteer
That would be when you have x^2-1=0 and you solve for zero
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volunteer
You get x=1 and x=-1 therefore domain is all real numbers except -1 and 1
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student
ok
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student
and you can have x^2-1=0 for this problem if we swicthed up the sign from + to -
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student
so then that would be domain for our problem if we had a diff sign
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volunteer
Yes but it would be a different problem at that point. Different problems give us different domains.
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volunteer
You can't switch signs in problems otherwise it will complicate future steps.
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student
yes but if we had 1-x^2 instead of 1+x^2
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student
that would be the domain
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student
for this problem
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student
if we subituted
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volunteer
Sure
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student
ok so im correct if we sub that would be domain
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student
for this equatiojn
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volunteer
Yes, if you change the denominator you get a different result for domain
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volunteer
The combinations are limitless
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student
ok
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student
just wanna make sure '
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student
for rational equations
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student
you can solve x^2-1=0
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student
in denom
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student
cause last time i think i said wanst solvable
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student
/no domain
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volunteer
Yes you can
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student
ok
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volunteer
Is that all, or do you have any other questions?
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student
thats all
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volunteer
I'll end the session here. Have a nice day!
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volunteer
Hello!
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