SOLUTION: Please help me solve {{{b^4 + b^2 - 20 = 0}}}

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Question 6533: Please help me solve b%5E4+%2B+b%5E2+-+20+=+0
Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
this is just a quadratic...let a=b%5E2, so the equation becomes

a%5E2+%2B+a+-+20+=+0

so, now factorise to (a+5)(a-4) = 0
--> a = -5 or a = 4

so b%5E2+=+4 or b%5E2+=+-5

so b = +2 or -2 or b = +sqrt%285%29i or -sqrt%285%29i

jon.