Question

Find the product:

(9x² − x + 15)(x² − 3)

Answer 1

By column method:

$$\begin{gathered} 9{\mathrm{x}}^2-\mathrm{x}+15 \\ \underline{\times ({\mathrm{x}}^2-3)} \\ 9{\mathrm{x}}^4-{\mathrm{x}}^3+15{\mathrm{x}}^2 \\ \underline{-27{\mathrm{x}}^2+3\mathrm{x}-45} \\ \mathrm{Add}:9{\mathrm{x}}^4-{\mathrm{x}}^3-12{\mathrm{x}}^2+3\mathrm{x}-45 \\ \therefore (9{\mathrm{x}}^2-\mathrm{x}+15)({\mathrm{x}}^2-3)=9{\mathrm{x}}^4-{\mathrm{x}}^3-12{\mathrm{x}}^2+3\mathrm{x}-45 \end{gathered}$$