Question

If x+y=8 and xy=5, then find the value of x2+y2

Answer 1

(x+y)2=X2+y2+2xy

(8)^2=X2+y2+2*5

64=X2+y2+10

54=X2+y2

mark me as brainlist

Answer 2

Given

x+y=8

xy=5

To find:

value of x square + y square

Solution:

x+y=8

x=8- y ----------(1)

BY SUBSTITUTING EQUATION 1 IN SECOND EQUATION, WE GET

(8-y)(y)=5

8y -y square=5

-y square+8y=5

y square -8y -5=0 ---------->quadratic equation

we should solve this by discriminant method

FORMULA

X=b + root of b square _4ac /2a

here

-(-8)+- root of 64-20 /2

8 +- root 44

_________

2

4+- root 11

the Answer is 4 + ^11 ; 4-^11.