-15=x+(x*x)
$(\frac{z-z^{-1}}{2})^4 $ simplified
cos(x) = 1,x
$(\frac{z+z^{-1}}{2})^4 $ simplified
sin((x+y)/2) = cos(x/2)
whai is the smallest number that 8 and 12 can divide without remainder
x.x-2x = -1
x = ?
x²\frac{dy}{dx}+3xy=\frac{1}{x}
expand these expressions 1.(c-2)(c+5)
