Question

find the value of 27x³+8y³if 3x+2y=20 and xy=14/9 ​

Answer 1

Answer: 7440

Explanation:

$3x+2y=20$

$\Rightarrow (3x+2y)^3 = 20^3$

$\Rightarrow (3x)^3+(2y)^3+3(3x)(2y)(3x+2y) = 8000$

$\Rightarrow 27x^3+8y^3+18xy(3x+2y) = 27x^3+8y^3+18(\frac{14}{9})(20) = 8000$

$\Rightarrow 27x^3+8y^3+560 = 8000$

$\Rightarrow 27x^3+8y^3=8000-560=7440$