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Mathematics 7 Online
OpenStudy (anonymous):

Simplify each radical expression. State any restriction on the variable.

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

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.

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)

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

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

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

jimthompson5910 (jim_thompson5910):

(x+5)(x+4) = 0 x+5 = 0 or x+4 = 0 x = -5 or x = -4

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