Solve: x^8-17x^4+16

You should treat the question as you would a normal quadratic and complete the square. First you should look at the factors of 16 and see which pair would result in the -17x; you can see that it would be -1 and -16. If it makes it easier, you could apply a substitution method, for example y^2 in the place of X^8 and y in place of x^4, so rewritten, the equation would look like; y^2 - 17y + 16 This can then be factorised to; (y-1)(y-16) so y=1,16 so x^4= 1, 16 so x= 1, 2