6 6/10 * 3/4 : 2 2/5 * 2 1/5 = 4 43/80
y=-2x^(5/6)-5x^(1/4)y'=-2*(5/6)*x^(5/6 - 1) - 5*(1/4) * x^(1/4-1) = -5/3 * x^(-1/6) - 5/4 * x^(-3/4)