SSC CGL 2021 PYQ — Question 57

The correct answer is option 2 i.e. - 1

We have given,

y = 2x + 1

y - 2x  = 1

Cube on both sides :

⇒ y³ - 8x³ - 3 × y² × 2x + 3  × y × 4x² = 1

⇒ y³ - 8x³ - 6xy(y - 2x) = 1

⇒ y³ - 8x³ - 6xy = 1                 {given y - 2x = 1}

multiply by (-1) in the above equation

8x³ + y³ + 6xy = -1