Question

solve: (x^2-3x)^2 - 16(x^2-3x) - 36=0

Answer 1

$x {}^{4} - 13x {}^{2} + 48 = 36 \\ x {}^{4} - 13x {}^{2} = - 12 \\ x {}^{2} (x {}^{2} - 13) = - 12$
is your answer