Answer:
C 14n - 8
Step-by-step explanation:
area of rectangle = length × width = 12n² - 19n - 21
width = 3n - 7
so, what do we need to multiply with width to get the expression of the area ?
4n + 3
(because we think, what do we need to multiply 3n with to get 12n², and what to multiply -7 to get -21)
control : (3n-7)×(4n+3) = 12n²-28n+9n-21 = 12n²-19n-21
perimeter is now 2× length + 2× width
p = 2(3n-7) + 2(4n+3) = 6n - 14 + 8n + 6 = 14n - 8
