Lets say , a is length and b is breadth of rectangle

Perimeter = 2(a+b) = 46

a+b = 23

b = 23 - a

Diagonal =

a^2 + a^2 + 529 - 46a = 289

2a^2 - 46a + 240 = 0

a^2 - 23a + 120 = 0

The value that we will get as a can be either length or breadth (as even if you solved for b you would have recieved same equaion)

Hence area = Lengt*Breadth = Multiplication of roots of this quadratic equation

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For an equation

lx^2 +mx +n = 0

Multiplication of roots = n/l

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So here it will be = 120