Question

if 2x+3y=13 and xy=6.find the value of 8x^3 +27y^3

Answer 1

793 and 5840 are the values ...

Answer 2

Hey!

Here is your answer!

(2x + 3y) = 13 (1)

xy = 6

To find :
$8x ^{3} + 27y {}^{3}$

Here we go!

On squaring both sides of (1)

$(2x + 3y) {}^{3} = (13) {}^{3}$
$2197 = 8x {}^{3} + 27y {}^{3} + 3(2x \times 3y)(2x + 3y)$
$2197 = 8x {}^{3} + 27y {}^{3} + 18xy(13)$
$2197 = 8x {}^{3} + 27y {}^{3} + 18 \times 6 \times 13$
$8x {}^{3} + 27y {}^{3} = 2197 - 1404$
$the \: answer \: is \: 793$


Hope it helps!