The area of a rectangle is represented by 12n2 - 19n - 21. If the width is 3n - 7, which expression represents the perimeter? A. 7n - 4
B. 7n+4
C. 14n -8
D. 14n +8

C 14n - 8

Step-by-step explanation:

rectangle area = length×width = 12n²-19n-21

width = 3n-7

what do we need to multiply with width to get the full area expression ?

think : what do we need to multiply with 3n to get 12n² (4n)?

and what to multiply with -7 to get -21 (3)?

=> length = 4n+3

perimeter is 2×length + 2×width

p = 2(3n-7) + 2(4n+3) = 6n-14+8n+6 = 14n-8

24

step-by-step explanation:

i assuming that 2 sides are 6 the other 2 sides are 4 cm so 6 times 4 is 24 : )