Question

What is the perimeter of the rectangle whose area =x2+3x-40?

Answer 1

Answer:

4x+6

Step-by-step explanation:

first we will factorise x^2+3x-40 to find the 2 sides

we can write it as x^2+8x-5x-40

=x(x+8)-5(x+8)

=(x-5)(x+8)

therefore 2 sides are x-5 and x+8

and perimeter = 2(x-5)+2(x+8)

=2x-10+2x+16

=4x+6

pls mark as brainliest

Answer 2

$\mathfrak{ \huge \underline \red{Question: - }} \\ \\ \purple{What \: is \: the \: perimeter \: of \: the \: rectangle \: whose } \\ \purple{ \: area \: = {x}^{2} +3x-40 \: ?} \\ \\ \mathfrak{ \huge \underline \red{solution: - }} \\ \\ \underline{given : - } \\ \\ the \: area \: of \: rectangele \: is \: \: \: \red{ {x}^{2} + 3x - 40} \\ \\ \underline{so \: now} \\ \\ = > \red{ {x}^{2} + 3x - 40} \\ \\ = > \red{ {x}^{2} + 8x - 5x- 40} \\ \\ = > \red{x(x + 8 ) - 5(x + 8)} \\ \\ = > \red{ (x + 8)(x - 5)} \: \: \: \: .......(1) \\ \\ = > \red{x = - 8 \: \: \: or \: \: x \: = 5 } \\ \\ \: value \: of \: x \: for \: perimeter \: is \: not \: in \: negative \: so \\ = > \red{x = 5 \: \: \: \: ..........(2)} \\ \\ \purple{let } \\ \\ \fbox{length \: (l) \: = (x + 8) \: \: and \: \: breadth \: (b) \: = (x - 5)} \\ \\ = > \red{perimeter \: of \: rectangle \: = 2(l+ b)} \\ \\ = > \red{perimeter \: of \: rectangle \: = 2( (x + 8)+ (x - 5) )} \\ \\ = > \red{perimeter \: of \: rectangle \: = 2( x + 8 + x - 5)} \\ \\ = > \red{perimeter \: of \: rectangle \: = 2(2x + 3 )} \\ \\ = > \red{perimeter \: of \: rectangle \: = 4x + 6 } \\ \\ from \: {eq}^{n} (2) \\ \\ = > \red{perimeter \: of \: rectangle \: = 4(5) + 6 } \\ \\ = > \red{perimeter \: of \: rectangle \: = 20+ 6 } \\ \\ = > \red{perimeter \: of \: rectangle \: = 26 units} \\ \\ \fbox{perimeter \: of \: rectangle \: is\: 26 \: units.}$