Expand $\left(x+3\right)\left(x-3\right)=x^2-$
$\quad$ Factorize $x^2-9=\bigl(x+$
$\bigl)\bigl(x-$
$\bigl)$
Expand $\left(x-7\right)\left(x+7\right)=x^2-$
$\quad$ Factorize $x^2-49=\bigl(x+$
$\bigl)\bigl(x-$
$\bigl)$
Expand $\left(x-4\right)\left(x+4\right)=$
$\quad$ Factorize $x^2-16=$
Expand $\left(5-x\right)\left(5+x\right)=$
$\quad$ Factorize $25-x^2=$
Expand $\left(2x+3\right)\left(2x-3\right)=$
$\quad$ Factorize $4x^2-9=$
Expand $\left(-5a+7b\right)\left(7b+5a\right)=$
Factorize $-25a^2+49b^2=$