Multiply Polynomials with Box Method - Examples & Practice

$3x^2$ and $-x^2$, and $4x$ and $9x$

$4x^2$ and $-x^2$, and $4x$ and $-9x$

$-9x^2$ and $3x^2$, and $-3x$ and $-9x$

$3x^2$ and $-6x^2$, and $-x$ and $-9x$