Answer:
Step-by-step explanation:
(9 + m)(-m + 9) = (9 + m)(9 - m) {(a+b)(a-b) = a² - b²}
= 9² - m²
= 81 - m²
= -m² + 81
Answer: -m^2+81
I used the foil method
(9+m)(-m+9)
first: 9*-m=-9m
second: 9*9=81
third: m*-m=-m^2
forth: m*9= 9m
then you do this: -9m+81-m^2
+9m
------------------
81-m^2
then you set at the decending powers of x. which will give you: -m^2+81
