4(x+5)(x+6)(x+10)(x+12)-3x²=0

4 (x+5) (x+6) (x+10) (x+12) − 3x^2 = 0

4x^4 + 132x^3 + 1565x^2 + 7920x + 14400 = 0

Factor left side of equation.

(x+8) (2x+15) (2x^2 + 35x + 120) =0

Set factors equal to 0.

x + 8 = 0 or 2x + 15 = 0 or 2x^2 + 35x + 120 = 0

x = −8

or x = − 15/2

or x = −4.6802948509750735

or x = −12.819705149