$$-x^2+6x+7=0$$

$$\sec^2\left(x\right)\tan^2\left(x\right)=\tan^4\left(x\right)+\tan^2\left(x\right)$$

$$-90\cdot40$$

$$5\left(2\right)\left(-1\right)+1$$

$$\frac{a^6-b^{12}}{a^2-b^3}$$

$$3-9\cdot6+4$$

$$10\sin\left(x\right)-6=4\sin\left(x\right)-9$$