Question

the length of a rectangle is 7 yd less than three times the width, and the area of the rectangle is 66 yd(squared). find the dimensions of the rectangle.

Answer 1

so legnt=l
width=w
l=-7+3w
l=3w-7

area=66
area=legnth times width or
area=lw

subisutte
area=lw
l=3w-7
66=(3w-7)(w)
66=3w^2-7w
subtrac 66 from both sides
0=3w^2-7w-66
factor
HOW TO
multiply 3 and -66=-198
find what 2 numbers add up to -7 and multiply to get -198
the numbers area 11 and -18
so
3w^2-18w+11w-66=0
factor
(3w^2-18w)+(11w-66)=0
(3w)(w-6)+(11)(w-6)=0
factor using distributive (ab+ac=a(b+c))

(3w+11)(w-6)=0
set them to zero
3w+11=0
subtract 11
3w=-11
legnths cannot be negative so we discard this

w-6=0
add 6
w=6

width=6
legnth=3w-7
length=3(6)-7
legnt=18-7
legnth=11


width=6
legnth=11