9)
(x+10)²
(x +10) (x+10)
We will take he x in the first bracket and then use it to multiply the second bracket
Also we will take the 10 in the first bracket and then use it to multiply the second bracket
That is:
x(x+10) + 10(x+10)
x² + 10x + 10x + 100
x² + 20x + 100