Question

Factorise x^4+2x^2+9

Answer 1

(x^2)^2+2x^2 +9=(x^2)^2 + 3x^2 +3x^2 +9 -4x^2 = x^2(x^2 +3)+ 3( x^2 +3)-4x^2= (x^2+3)^2 - (2x)^2 =(x^2 +3-2x)(x^2+3+2x)