1
(a²+3)/a³-(3-a)/3a=(3a²+9-3a²+a³)/3a³=(a³+9)/3a³
2
x/(x-1)+x/(x+1)=(x²+x+x²-x)/(x²-1)=2x²/(x²-1)
3
x/(x-2y)-4y²/x(x-2y)=(x²-4y²)/x(x-2y)=(x-2y)(x+2y)/x(x-2y)=(x+2y)/x
4
2a+b -4ab/(2a+b)=(4a²+4ab+b²-4ab)/(2a+b)=(4a²+b²)/(2a+b)
1 -cosa^2= sina^2
Sin a<1
1- 25/169= 144/169
Sina = -12/13
6x(x-y)+y(x-y)=(x-y)(6x+y)