1) -5,52:1,4 = -552/52 : 14/10 = -552·10/14 = - 276/70
2)-276/70·7/8 =- 69/20 = -3 9/20 = -3,45
3) 6,8 - 3,45 = 3,35
4y+9x=10
7x+2y=0|×(-4)
4y+9x=10 + -14x-4y=0
-5x=10
x=-2
7×(-2)+2y=0
-14+2y=0
2y=14
y=7
Ответ: x=-2 y=7
<span>2)sin(-a)cos(-a)(tg a+ctg a)=-sina cosa(sina/cosa +cosa/sina)=-sina cosa{(sin^2a+c0s^2a)/sinacosa}=-1</span>
X1=2; x2=5
(x-2)(x+5)=x²+5x-2x-10=x²+3x-10