$$\left(x-7\right)^2\left(x+7\right)^2-2\left(x^2-3\right)$$

$$\frac{d^2y}{dx^2}=\sin3x+\cos3x$$

$$25n^2-121m^2$$

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

$$6x^4-3x^4+7x^4$$

$$\frac{1}{x}<16$$

$$\int\left(2x+1\right)\left(x^{2}+x\right)dx$$