Question

The sum of any two number is 21and the sum of their squares is 261.find the numbers.​

Answer 1

The two numbers are 6 and 15.

Explanation:

`x+y=21\\y=21-x\\x^(2) +y^(2) =261\\x^(2) +(21-x)^(2)=261\\x^(2) +441-42x+x^(2) =261\\2x^(2) -42x+180=0\\x^(2) -21x+90=0\\(x-6)(x-15)=0\\`

x=6 and x=15