Arectangular deck is 12 ft by 14 ft. when the length and width are increased by the same amount, the area becomes 288 sq. ft. by how much were the dimensions increased?
a-2ft
b-4ft
c-8ft
d-10ft

X=amount increased

newlegnth=legnth+x=14+x
newwidth=width+x=12+x

area=legnth times width
newarea=newlegnth times newwidth

288=newarea

(14+x)(12+x)=288
168+26x+x^2=288
x^2+26x+168=288
minus 288 from both sides
x^2+26x-120=0
factor
find what 2 numbers multiply to get -120 and add to get 26
-4 and 30
(x-4)(x+30)=0
set each to zero

x-4=0
x=4

x+30=0
x=-30
wrong, if it was increased by -30, the side legnths would be -18 and -16, and negative measures are not allowed

x=4

answer is increased each side by 4 feet

B