x₁ = - 4 + 3√2
x₂ = - 4 - 3√2
Hi !
2x² + 16x - 11 = - 7
2x² + 16x - 11 + 7 = 0
2x² + 16x - 4 = 0 | : 2
x² + 8x - 2 = 0
a = 1 ; b = 8 ; c = - 2
x = (- b ± √b² - 4ac)/2a
x = (-8 ± √8² - 4×1×-2)/2×1
x = 2(-4 ± √3√2)/2
x = - 4 ± 3√2
x₁ = - 4 + 3√2
x₂ = - 4 - 3√2
Good luck !