9 и -1
ход решения
1)х = 8 - у
2)24 - 3у - 4у = 31
-7у = 31 - 24
-7у=-7
у=-1
3)х=8+1
х=9
1) 7x-39=2(x+3)+6-2x+5 = 7x-39=2x+6+6-2x+5= 7x=56 x=8
2) 3(x-5)=5(x-3)-4(2-3x) = <span>3x-15=5x-15-8+12x= -14x=-8 14x=8 x=1,75</span>
<span>основное sin^2 x + cos^ x =1
1-sin^2a = cos^2 a
1-cos^2a = sin^2 a
sin^2a-1 = sin^a- (cos^2a +sin^2a)=-cos^2a
cos^2a-1=cos^2a-(cos^a+sin^2a)=-sin^2a</span>
(4x-3)*3 - 2x = 18
12x - 9 - 2x = 18
10x = 27
x = 27/10
x = 2,7
6sin20 6*2*sin10*cos10 12sin10 12 sin10
-------------------- = -------------------------- = ------------------ = ---------------- = 12
cos10*cos80 cos10*cos80 cos(90-10) sin10