3^(x + 1) - 3^x = 18
3*(3^x) - 3^x = 18
2*(3^x) = 18
3^x = 9
3^x = 3^2
x = 2
(x2+xy) / (x2-y2) = x(x+y) / (x-y)(x+y) = x/ (x-y) = 1 / (x/x -y/x) = 1 / (1 -y/x)
x=2,4,y=0,4
1 / (1 -0,4/2,4) = 1 / (1 -1/6) = 1 / (5/6) = 6/5 = 1,2
ответ 1,2
(a-b)(a+b)=a²-b²
--------------------------------------
(9x-3)(9x+3)-81x²-7x+9=81x²-9-81x²-7x+9=-7x
x=140 -7*140=-980
Sin5П*cosx-sinx*cos5П=cos2x*cos7П-sin2x*sin7П
sinx=-cos2x
sinx=sin^2(x)-cos^2(x)
sinx=sin^2(x)-1+sin^2(x)
2sin^2(x)-sinx-1=0
sinx=y,-1<=y<=1
2y^2-y-1=0
y1=1,y2=-1/2
sinx=1
x=π/2+πn
или
sinx=-1/2
x=(-1)^n*arcsin(-1/2)+πn=(-1)^n*(-π/6)+πn
b≥0
(b-b)x=b+b
0x=2b
х любое число
b<0
(b+b)x=b-b
2bx=0
x=0