Question

if x+y=8, xy= 15÷4 and x-y is 7 then 3(x×x+y×y) =

Answer 1

x+y=8
x-y=7
by adding both equations
2x=15
x=15/2
.
xy=15/4
15/2*y=15/4
y=15/4*2/15
y=1/2
.
3(15/2*15/2+1/2*1/2)
3(225/4+1/4)
3(226/4)
3(56.5)
169.5

Answer 2

__________

As,

x +y = 8 

square on both sides,

(x + y )² = 8²

x² + y² + 2xy = 64 

x² + y² + 15/2 = 64

x² + y² = 64 -15/2 

x² + y² = (128 - 15)/2

x² +y² = 113/2  -----1equation 
__________

3(x² + y²) = 3(113/2)

3(x² + y²) = 339/2





i hope this will help you



-by ABHAY







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