SOLUTION: #8. x^4 + 5x^2 -36 = 0 I started working this problem and then got confused. If you could help with this. Thanks

Question 191938This question is from textbook College Algebra A Graphing Approach
: #8. x^4 + 5x^2 -36 = 0
I started working this problem and then got confused. If you could help with this. Thanks This question is from textbook College Algebra A Graphing Approach

Found 2 solutions by nerdybill, RAY100:
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
x^4 + 5x^2 -36 = 0
Factoring:
(x^2+9)(x^2-4) = 0
.
Setting each term to zero:
(x^2+9) = 0
x^2 = -9
x = sqrt(-9)
x = +- 3i
.
(x^2-4) = 0
x^2 = 4
x = sqrt(4)
x = +- 2

Answer by RAY100(1637) (Show Source): You can put this solution on YOUR website!
x^4+5x^2-36=0
usually we do x^2+x-4 =0 for example
but just use same tech
(x^2 -4) (x^2 +9)=0
use FOIL to check
now lets look further
(x^2-4) is pattern for difference of squares so
(x+2) (x-2) is that factor
unfortunately x^2 +9 looks factorable but is not
in summary
(x+2) (x-2) (x^2+9) =0
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