(-4xy^{3}) × (6x^{2}y) = (-4 × 6) (x ×x^{2}) (y^{3} × y) = -24x^{3}y^{4}
For x = 2 and y = 1
(-4xy^{3}) × (6x^{2}y) = (-4 × 2 × 1^{3}) × (6 × 2^{2 }× 1)
= (-8) × 24 = -192
And, -24x^{3}y^{4 }= -24 × 2^{3} × 1^{4}
= -24 × 8 × 1 = -192
∴ For x = 2 and y = 1, it is verified that
(-4xy^{3}) × (6x^{2}y) = -24x^{3}y^{4}