$$cos8x-cos7x$$

$$f\left(-7\right)=4x^2-4x$$

$$54.3=\frac{2x^2}{\left(0.15-x\right)\left(0.09-x\right)}$$

$$4x^2+8x-5$$

$$\frac{sec\left(x\right)}{sec\left(x\right)-tan\left(x\right)}=sec\left(x\right)\left(sec\left(x\right)+tan\left(x\right)\right)$$

$$y^3+sy^2$$

$$\frac{142.14}{142}$$