X+y=5*3x^2+3y^2=35
x+y=15x^2+3y^2=35
x+y=3(5x^2+y^2)=35
x^2=A
y^2=B
x+y=3(5A+B)=35
15A+3B=35
15A+3B-35=0|
5)А
=1/2[cos(x+x/2) +cos(x-x/2)]-1/2[cos(x-x/2)-cos(x+x/2]
=1/2[cos(x+x/2) +cos(x-x/2)-cos(x-x/2)+cos(x+x/2)]
=1/2[2cos(x+x/2)]
=cos 3x/2
А)y=4x-30
y=4•(-2,5)-30
y=-10-30=-40
y=-40
б)-6=4x-30
4x=-30+6
4x=-24
x=-24:4
x=-6
Я решил, вроде равно нуль