Question 130076
x*y=18 or x=18/y
2x+2y=18 now replace x by (18/y) & solve for y:
2(18/y)+2y=18
36/y+2y=18
(36+2y^2)/y=18 now cross multiply
36+2y^2=18y
2y^2-18y+36=0
2(y^2-9y+18)=0
2(y-6)(y-3)=0
y-6=0
y=6 answer
y-3=0
y=3 answer.
so the sides of this rectangle are 3 & 6 cm.
proof:
3*6=18
2*(18/6)+2*3=18
36/6+6=18
12+6=18
18=18