If $x^2+4 y^2=53$ and $x-2 y=5$, then what is the value of $x^3-8 y^3$ ?

155 335 -85 85

335

If $x^2+4 y^2=53$ and $x-2 y=5$, What is the value of $x^3-8 y^3$  ( a - b )2 = a2 + b2 - 2×2ab (5 )2 = 53 - 4ab 4ab = 28 ab = 7 If x - y  = n then, $x^3 - y^3$ = n3 + 3 × n × xy $x^3-8 y^3$   = 53 + 3 × 5 × 2 × 7 $x^3-8 y^3$  = 125 + 210 $x^3-8 y^3$   = 335