Mathematics
7 Online
OpenStudy (anonymous):
Simplify each radical expression. State any restriction on the variable.
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OpenStudy (anonymous):
\[\frac{ x^2 + 10x + 25 }{ x^2 + 9x + 20 }\]
jimthompson5910 (jim_thompson5910):
This is a rational expression since rational expressions are fractions of polynomials.
Anyways, are you able to factor the top or bottom?
OpenStudy (anonymous):
yes i think so
OpenStudy (anonymous):
the top would be (x +5^2)
jimthompson5910 (jim_thompson5910):
ok show me what you get when you factor each
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jimthompson5910 (jim_thompson5910):
close but no
OpenStudy (anonymous):
The bottom would be (x + 5)(x + 4)
jimthompson5910 (jim_thompson5910):
the top should be (x+5)^2 which is the same as (x+5)(x+5)
jimthompson5910 (jim_thompson5910):
the bottom is correct
OpenStudy (anonymous):
I'm not sure what to do next.
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jimthompson5910 (jim_thompson5910):
what terms do you notice in common between top and bottom?
OpenStudy (anonymous):
the (x + 5)
jimthompson5910 (jim_thompson5910):
those will cancel because they divide to 1
jimthompson5910 (jim_thompson5910):
and because x*1 = 1*x = x
OpenStudy (anonymous):
So it would just be (x + 5)/(x + 4)
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OpenStudy (anonymous):
Thanks!
jimthompson5910 (jim_thompson5910):
yes
jimthompson5910 (jim_thompson5910):
`State any restriction on the variable.`
OpenStudy (anonymous):
Idk how to do that part..
jimthompson5910 (jim_thompson5910):
hint: you cannot divide by zero
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OpenStudy (anonymous):
Would the restriction be how there was two (x + 5)?
jimthompson5910 (jim_thompson5910):
what values of x make the denominator zero?
OpenStudy (anonymous):
x + 4
jimthompson5910 (jim_thompson5910):
(x+5)(x+4) = 0
x+5 = 0 or x+4 = 0
x = ??? or x = ???
OpenStudy (anonymous):
neither it's not equal
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jimthompson5910 (jim_thompson5910):
if x+5 = 0, then what must x be?
OpenStudy (anonymous):
-5
jimthompson5910 (jim_thompson5910):
and if x+4 = 0 then x is what?
OpenStudy (anonymous):
-4
jimthompson5910 (jim_thompson5910):
so if either x = -5 or x = -4, then the entire denominator will be zero
therefore we have to exclude those values to avoid dividing by zero
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jimthompson5910 (jim_thompson5910):
(x+5)(x+4) = 0
x+5 = 0 or x+4 = 0
x = -5 or x = -4