If x = 2 and y = 1 ; find the value of (-4x²y³) x (-5x²y⁵).

(-4x²y³) $\times$ (-5x²y⁵)

= (-4) $\times$ (-5)x⁽²⁺²⁾y⁽³⁺⁵⁾

= 20 x⁴y⁸

When x = 2 and y = 1,

= 20 x 2⁴ x 1⁸

= 20 x 16 x 1

= 320

Hence, if x = 2 and y = 1 ; the value of (-4x²y³) x (-5x²y⁵) = 320.