Factorization

a²-b²=(a+b)(a-b)

$$\textup{Factorize } x^2-16 $$

\begin{align*} &\because\;\; a^2-b^2=(a+b)(a-b) \\\\ &\therefore\;\; x^2-16 \\ &=(x)^2-(4)^2 \\ &=(x+4)(x-4) \\ \end{align*}

$$\textup{Factorize } y^2-25 $$

\begin{align*} &\because\;\; a^2-b^2=(a-b)(a+b)\\\\ &\therefore\;\; y^2-25 \\ &=(y)^2-(5)^2 \\ &=(y-5)(y+5) \\ \end{align*}

$$\textup{Factorize } 4x^2-9 $$

\begin{align*} &\because\;\; a^2-b^2=(a+b)(a-b) \\\\ &\therefore\;\; 4x^2-9 \\ &=(2x)^2-(3)^2 \\ &=(2x+3)(2x-3) \\ \end{align*}

$$\textup{Factorize } 25y^2-16 $$

\begin{align*} &\because\;\; a^2-b^2=(a-b)(a+b)\\\\ &\therefore\;\; 25y^2-16 \\ &=(5y)^2-(4)^2 \\ &=(5y-4)(5y+4) \\ \end{align*}