Question

calcule x

7×-10° ×+20°

Answer 1

7x - 10º . X + 20º
(7x - 1) . (X + 1)
7x² + 7x - x - 1 = 0
7x² + 6x - 1 = 0
∆ = b² - 4ac
∆ = 36 - 4 . 7 .(-1)
∆ = 36 +28
∆= 64

X = (-b +-√64)/2a
X = (-6 +- 8)/2.7
X = ( -6 +-8)/14

X' = (-6+8)/14 = 2/14 = 1/7

X" = (-6-8)/14 = -14/14 = -1

X = -1, 1/7