Question

What is the completely factored form of x4 + 8x2 – 9?

Answer 1

${x}^{4} + 8 {x}^{2} - 9 \\ = {x}^{4} + 9 {x}^{2} - {x}^{2} - 9 \\ = {x}^{2} ( {x}^{2} + 9) - 1( {x}^{2} + 9) \\ = ( {x}^{2} + 9)( {x}^{2} - 1) \\ = ( {x}^{2} + 9)(x - 1)(x + 1) \\ so \: \: {x}^{2} = - 9 \: but \: that \: is \: not \: possible \\ so \: x = 1 \: \: \: or \: \: \: x = - 1$
So that's the answer