a) (3x-5)*(2x+1)+(7x-5)^2 = -2 6x^2+3x * -10x-5 +49x - 25 = -2 6x^2+3x * -59x-30 = -2 /:x (6x+3) * (-59-(30/x)) = -2/x (6x+3) * (-29/(1-x)) = -2/x /: (-29/(1-x)) 6x+3 = (-2/x)/(29/(1-x)) /*(1-x) 12x^2 = (-2/x)/29 /*x 12x^3 = -2/29 /*29 348x^3 = -2 /:348 x^3 = -2/348 x = ∛(-2/348) b) -2² + 3x + 5 ≥ 0 4 + 3x + 5 ≥ 0 9 + 3x ≥ 0 c) (x+1)*(x-3) ≥ 0 x((1+1)*(1-3)) ≥ 0 x(2*(-2)) ≥ 0 -4x ≥ 0 d) 2(x+1)²-(x-3)² ≥ 11x-1 2(x^2 +1)-(x^2 - 9) ≥11x-1 2x^2 + 2 - x^2 + 9 ≥ 11x-1 2 + 2 +9 ≥ 11x-1 13 ≥ 11x-1 /+1 14 ≥ 11x /:11 14/11 ≤ x x ≥ 14/11
