D = b^2 - 4ac
D = 6^2 - 4 * (-1) * 7 = 36 + 28 = 64
x1 = (-b + sqrt(D))/a
x2 = (-b - sqrt(D))/a
x1 = (6 + 8)/(-2) = 14/(-2) = -7
x2 = (6 - 8)/(-2) = -2/(-2) = 1
=-1+1-0,5=-0,5
..................... Ответ:б
Решение на фото..........................
1) (2а-b²)(2а+b²)= 4а²-b⁴
2) (х-6х³)²= x²- 12x⁴ +36x⁶
3) (у+b)²(у-b)²= (у+b)(у-b)(у+b)(у-b) = (у²-b²)(у²-b²) = (у²-b²)² =
= y⁴-2y²b²+ b⁴