3 уравнение:
х+у=49
-х+у=17
1)х+у=49
у=49-х
2)-х+49-х=17
-2х+49=17
-2х=49-17
-2х=-32
х=-32: (-2)
х=16
3)у=49-16=33
Проверка: 16+33=49
Ответ: (16;33)
1) (5a-c)*(5a+c)
2) (3x-4y)*(3x+4y)
3) (x-2y)*(x+2y)
4) (x-2y)*(x^2+4y^2)
5) (3a-4b)*(9a^2+16b^2)
50x-56x+224=104
-6x=-120
x=20
4sin(20°)sin(40°)sin(60°)sin(80°)=2sin(20°)sin(40°)√3*sin(80°=(cos(-20°)-cos(60°))√3*sin(80°)=(cos(20°)-1/2)√3*sin(80°)=√3/2*(2sin(100°)+√3)/(2)-(√3*sin(80°))/2=2√3sin(100°)+3-2√3sin(80°)=0,75