Решите уравнение (5х - 1) (5х + 1) – (5х – 6)2 = 20

Question

Решите уравнение (5х - 1) (5х + 1) – (5х – 6)2 = 20

Answer 1

25х^2 - 10x +12 -20 = 0
25x^2 - 10x - 8 = 0 
D = 100 + 800 = 900 > 0
x = 0.8   x = -0.4