10•(3а-b)-17•(2a+b) = 30а -10b - 34 a - 17b = - 4a - 27b= -4×3 - 27×4= -12 -108 = -120
А 12 = -5,5+4,1*12 = 43,7
(3y-2)(5y+3)-(2y+1)(7y-2)=-4
15у^2-10у+9у-6-14у^2-7у+4у+2=-4
у^2-4у=0
у(у-4)=0
у=0 и у=4
k≠-4 k≠4
1/(k - 4) - 9/(k + 4) = 1/(k-4)*9/(k+4)
k + 4 - 9(k - 4) = 9
k + 4 - 9k + 36 = 9
-8k = -31
k = 31/8