(x^2+6x)^2+8(x^2+6x)-9=0​

Question

(x^2+6x)^2+8(x^2+6x)-9=0​

Answer 1

x^2+6x=z

z^2+8z-9=0

D/4=16+9=25

z1=-4+5=1 (1)

z2=-4-5=-9 (2)

(1) z1=x^2+6x=1

x2+6x-1=0

D/4=9+1=10

x1=-3+V10

x2=-3-V10

(2) z2=x^2+6x=-9

x^2+6x+9=0

D/4=9-9=0

x3=-3