Question

How do you multiply `\frac { 9- d ^ { 2} } { d + 3} \cdot \frac { d } { d - 3}`?

Answer 1

`-d`

Explanation:

`(9-d^2)/(d+3) xxd/(d-3)" "larr` factor diff of squares

`(cancel((3+d))color(blue)((3-d)))/(cancel((d+3))) xx d/((d-3))" "larr(3+d)=(d+3)`

Do a sign "switch-round"

`(color(blue)(-(d-3)))/1 xx d/((d-3))" "larr color(blue)((3-d) = -(d-3))`

`(-(cancel(d-3)))/1 xx d/(cancel((d-3)))" "larr` cancel like factors

`=-d`