Question

$\left(x+3\right)\left(x+7\right)$. Solve using identity.

Answer 1

Solve using identity

Use the algebraic identity:

$(x+a)(x+b)=x^2+(a+b)x+ab$

Then,

$$\begin{gathered} (x+3)(x+7)=x^2+(3+7)x+3\times 7 \\ =x^2+10x+21 \end{gathered}$$

Therefore, $(x+3)(x+7)=x^2+10x+21$