54-12x+8>=70-20x
8x>=8
x>=1
4-14x-4>=-4x-90
x<=9
1. D=1+8=9=3^2>0
X1=(1+3)/2=2
X2=(1-3)/2=-1
Ответ: 2;-1
2. D=4+12=16=4^2
X1=(2+4)/2=3
X2=(2-4)/2=-1
Ответ: 3;-1
(x+7)²-(x-4)(x+4)= x²+14x+49-x²+16= 14x+65
А) x^3 - 9x = x(x^2 - 9) = x(x-3)(x+3)
Б) -5a - 10 ac - 5c^2 = -5 (a + 2ac + c^2)
В) 16x^4 -81 = (4x^2 + 9)(2x-3)(2x+3)
Г) x^2 - x - y^2 - y = (x^2-x) - (y^2 + y) = x(x - 1) - y(-y-1)