Question

if the area of a rectangle is 243m² and the length is 4b-9 (b-base)
find it's perimeter (pls. with steps)

Answer 1

l=4b-9 
area=243
l×b=243 (4b-9)b=243 
4b²-9b-243=0 
4b²-36b+27b-243=0 
4b(b-9)+27(b-9)=0 
(b-9)(4b+27)=0 
b=9,-27/4 
base can't be negative so b=9 and 
l=4×9-9=27 
so perimeter=2*(l+b)=2*(9+27)  =70