2cosa+7sina=0
7sina=-2cosa
7tga=-2
tga=-2/7
49+4=53
sina=-2/sqrt(53)
cosa=7/sqrt(53)
f(min)=(-4-49)/sqrt(53)=-sqrt(53)
A)2x+3=3x-7 b)9x-2=5x-2 в)10-3x=2x-15
2x-3x=-7-3 9x-5x=0 3x+2x=15+10
-1x=-10 нет решений 5x=25
x=10 x=5
17-2(x+3)+5(x-7)-3(2x+1) = 30
17-2*x-2*3+5*x-5*7-3*2*x-3*1 = 30
-27 - 3*x = 30
-3*x = 57
x = -19