What are the solutions of the equation x^4-9x^2+8=0? use u substitution to solve

Answer with Step-by-step explanation:

We have to solve the equation:

let u=x²

u²-9u+8=0

⇒ u²-8u-u+8=0

⇒ u(u-8)-1(u-8)=0

⇒ (u-8)(u-1)=0

⇒ u=8 or u=1

⇒ x²=8 or x²=1

⇒ x=2√2 or x=-2√2 or x=1 or x=-1

Hence, Solution of is:

x=2√2 ,-2√2,1 and-1

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step-by-step explanation: