SOLUTION: Find the solution of the Equation of 4x^4-5x^2-9=0 by using u- substitution method.

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Question 896219: Find the solution of the Equation of 4x^4-5x^2-9=0 by using u- substitution method.
Answer by josgarithmetic(39629) About Me  (Show Source):
You can put this solution on YOUR website!
u=x%5E2

4u%5E2-5u-9=0
%284u-9%29%28u%2B1%29=0

EITHER 4x%5E2-9=0
4x%5E2=9
x%5E2=9%2F4
highlight%28x=-3%2F2%29 OR highlight%28x=3%2F2%29
OR
x%5E2%2B1=0
x%5E2=-1
x=-sqrt%28-1%29 or x=sqrt%28-1%29
highlight%28x=-i%29 or highlight%28x=i%29