$2.6\cdot10$

$\left(x^2+5x\right).\left(x^2-5x\right)$

$f\left(x\right)=\left(5x^2+2x-2\right)^2$

$3x\left(x^2+2x\right)+5x\left(5x-3x^2\right)$

$sec^2x+3=tan^2x+4$

$\frac{dy}{dx}=7y,\:y\left(0\right)=-8$

$\log\left(x\right)=\frac{5}{2}\log\left(16\right)-\frac{2}{3}\log\left(8\right)$