=3x2+5x-1=x2-4x
3x2+5x-1-x2+4x=o
2x2+9x-1=o
Х=2-у
3х-2у-11=0
х=2-у
3(2-у)-2у=11
х=2-у
6-3у-2у=11
х=2-у
-5у=5
х=2-у
у=-1
х=3
у=-1
1/2(cos70-cos90)1/2(cos50-cos90)=1/4cos50cos70
cos90=0
cos70cos50=cos70cos50
1
6ab²91-2b)
2
2a(a²-4)=2a(a-2)(a+2)
3
3c(a²-c²)=3c(a-c)(a+c)
4
9mn(2n+3m)
5
(10x-1)(10x+1)
6
2(y²-6y+9)=2(y-3)²