Whats the answer to -84= -10b - 4

b = 8

Step-by-step explanation: -84 = -10b - 4

Add 4 to both sides -80 = -10b

Divide both sides by -10      8 = b

A= π (n + 4) ^2
= π (n + 4) (n + 4) 

remember order of operations FOIL 

= π  (n^2 + 4n + 4n + 16)
= π (n^2 + 8n + 16)

A= πn^2 + 8πn + 16π

do the same for B just change the signs 

B = πn^2 - 8πn + 16π 

subtract the two 

(πn^2 + 8πn + 16π) - (πn^2 - 8πn + 16π) 

=16πn