Question

x+y = 8 and xy = 15/4 find 3(x^2+y^2)

Also please tell me how to mark an answer as brainliest (android app), so that i can mark it as brainliest.

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Answer 1

Step-by-step explanation:

Refer to the attachment..........

If you ask a question and someone answered it, three or four days later you receive a notification in which you can mark an answer as brainliest.

Answer 2

Answer:

Step-by-step explanation:

To find 3($x^{2}$ + $y^{2}$)

x + y = 8

xy = 15/4

Step 1 = Make x + y = 8 whole square both the sides so that we could find the value of 3($x^{2}$ + $y^{2}$)

That is,

$(x + y)^ {2}$ = $(8)^{2}$

Now

Follow the identity

$x^{2}$ + 2xy + $y^{2}$[Using identity $(a + b)^{2}$ = $a^{2}$ + 2ab + $b^{2}$] = 64($8^{2}$ or 8 X 8= 64)

xy = 15/4(Given)

$x^{2}$ + 2xy + $y^{2}$ = 64

$x^{2}$ + 2(15/4)[As xy = 15/4] + $y^{2}$ = 64

$x^{2}$ + 15/2 + $y^{2}$ = 64

Follow the rules of linear equation

$x^{2}$ + $y^{2}$ = 64 - 15/2

Take L.C.M of the denominators 1 and 2

That is 2

64/1 X 2/2 and 15/2 X 1/1[To make the denominators equal]

128/2 and 15/2

CONTINUE

$x^{2}$ + $y^{2}$ = 64 - 15/2

$x^{2}$ + $y^{2}$ = 128/2 - 15/2

$x^{2}$ + $y^{2}$ = 128 - 15/2

$x^{2}$ + $y^{2}$ = 113/2

Value of

3($x^{2}$ + $y^{2}$) = 3(113/2)[As $x^{2}$ + $y^{2}$ = 113/2]

3($x^{2}$ + $y^{2}$) = 339/2

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