Solve for: 9y^4-49

Expression: $9{y}^{4}-49$

Write the number in the exponential form with an exponent of $2$

${3}^{2}{y}^{4}-49$

Factor the number $4$

${3}^{2}{y}^{2 \times 2}-49$

Write the number in the exponential form with an exponent of $2$

${3}^{2}{y}^{2 \times 2}-{7}^{2}$

Use ${a}^{mn}={\left( {a}^{n} \right)}^{m}$ to transform the expression

${3}^{2} \times {\left( {y}^{2} \right)}^{2}-{7}^{2}$

Multiply the terms with equal exponents by multiplying their bases

${\left( 3{y}^{2} \right)}^{2}-{7}^{2}$

Use ${a}^{2}-{b}^{2}=\left( a-b \right)\left( a+b \right)$ to factor the expression

$\left( 3{y}^{2}-7 \right) \times \left( 3{y}^{2}+7 \right)$