Question

Разложите на множители ( 10 класс)
а) x²-4x-21
b) -3x² + 12x +15
c)5y²-3y-2

Answer 1

а) D = 16 + 84 = 100 = 10^2
x1 = 7
x2 = -3
x^2-4x-21 = (x-7)(x+3)
б) D = 144 + 180 = 324 = 18^2
x1 = -1
x2 = 5
-3x^2+12x+15 = -3(x+1)(x-5) = (x+1)(15-3x)
в) D = 9 + 40 = 49 = 9^2
y1 = 1,2
y2 = -0,6
5y^2-3y-2 = 5(y-1,2)(y+0,6) = (y-1,2)(5y+3)