Then the other number is (15 – x) Let S(x)
denote the sum of the squares of these numbers Then
Rationalised 2023-24
 MATHEMATICS
168
S(x) = x2 + (15 – x)2 = 2x2 – 30x + 225
or
S ( )
4
30
S ( )
4
x
x
x
′
=
−

 ′′
=

Now S′(x) = 0 gives 
x =215 Also 
15
S
4
0
2

′′
=
>



