((1/14)x²x² - 14y²)²
((9/4)a³ - 2b²)²
1/2(cos(x+30-x+30)-cos(x+30+x-30)=1/4-sin^2x
6x+18+6x+12=5*(x+2)(x+3)
12x+30=30+5x^2+25x
5x^2+13x=0
x1=0
x2=-13/5=-2,6
l=2.6