Square

[kate]

If we decrease the side of a square with 9 cm, its area will be decreased with 189 cm ².The perimeter of the square is?

[Guest]

suppose the side of square is a
so area =[tex]a^{2}[/tex]
new side =a-9
new area=[tex](a-9)^{2}[/tex]
according to statement
new area=old area -189
[tex](a-9)^{2}=a^{2}-189[/tex]
[tex]a^{2}+9^{2}-2(a)(9)=a^{2}-189[/tex]
[tex]a^{2}+81-18a=a^{2}-189[/tex]
81-18a=-189
18a=81+189
18a=270
a=15
so the perimeter =4a=4*15=60


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