Answer:
Step-by-step explanation:
x² + 3x - 70 = 0
x² + 3x = 70
x² + 3x + (3/2)² = 70 + (3/2)²
(x + 3/2)² = 70 + 9/4 = 289/4 = (17/2)²
so
x + 3/2 = ±17/2
x = ±17/2 - 3/2
x₁ = 17/2 - 3/2 = 14/2 = 7
x₂ = -17/2 - 3/2 = -20/2 = -10
x² = -10x - 30
x² + 10x = -30
x² + 10x + (10/2)² = -30 + (10/2)²
x² + 10x + 25 = -30 + 25 = -5
(x + 5)² = -5
[tex]x+5 = \pm\sqrt{-5}\\x + 5 = \pm i \sqrt{5}\\x = -5\pm i \sqrt{5}\\\\x_1 = -5+ i \sqrt{5}\\\\x _2= -5- i \sqrt{5}\\[/tex]
