Sagot :
If the area of the rectangle is 40 square centimeters and length is 7 cm less than 3 times the breadth then the length will be 8 cm and breadth will be 5 cm.
Given area of the rectangle is 40 square centimeters and length is 7 centimeters less than 3 times the breadth.
let the breadth of rectangle be x.
According to question
Length=3x-7
Breadth=x
Area of rectangle=length* breadth
=[tex](3x-7)x[/tex]
=[tex]3x^{2} -7x[/tex]
Area is given as 40 square centimeters.
40=[tex]3x^{2} -7x[/tex]
[tex]3x^{2} -7x-40=0[/tex]
By factorization
[tex]3x^{2} -15x+8x-40=0[/tex]
3x(x-5)+8(x-5)=0
(3x+8)(x-5)=0
3x+8=0
x=-8/3
x-5=0
x=5
We should neglect x=-8/3 because side cannot be negative. So we have taken x=5.
Put x=5 in 3x-7 to get length
length=3(5)-7
=15-7
=8
Hence the length will be 8 cm and breadth will be 5 cm.
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