91Ó°ÊÓ

Multiply and simplify each of the following. Whenever possible, do the multiplication of two binomials mentally. $$\left(x^{2}+x+1\right)\left(x^{2}+x-1\right)$$

Multiply out each of the following. As you work out the problems, identify those exercises that are either a perfect square or the difference of two squares. $$(t+6)(t-6)$$

Simplify each of the following as completely as possible. $$2\left(r^{3} s^{5}\right)^{4}$$

Multiply and simplify each of the following. Whenever possible, do the multiplication of two binomials mentally. $$\left(u^{2}+2 u+1\right)\left(u^{2}-2 u+1\right)$$

Convert each number into scientific notation. $$0.0025 \times 10^{-4}$$

Simplify each of the following expressions as completely as possible. Final answers should be expressed with positive exponents only. (Assume that all variables represent positive quantities.) $$10^{7} 10^{-5}$$

Multiply out each of the following. As you work out the problems, identify those exercises that are either a perfect square or the difference of two squares. $$(c-4)^{2}$$

Simplify each of the following as completely as possible. $$\left(-x^{3} y\right)^{3}$$

Convert each number into standard notation. $$2.8 \times 10^{4}$$

Simplify each of the following expressions as completely as possible. Final answers should be expressed with positive exponents only. (Assume that all variables represent positive quantities.) $$10^{6} 10^{-5} 10^{-4}$$