solve for 1-tan^2x / 1+tan^2x
9(1+9^x-1)=10*3^x
5x+3+x+4
3^(2x+1)=54
18:x+4=9:x-3
3-(1+6a)
(5z-2)/3 - (4z-4)/2 = (2z+1)/3
5^(x+1)-3/25=2.5^x
solve x
(64-x^2)^3
