Question 33: Calculate the value of the expression \(\begin{array}{l} A = \left( {15{x^5}{y^3} – 10{x^3}{y^2} + 20 {x^4}{y^4}} \right):5{x^2}{y^2} \end{array}\) at x=-1, y=2.

\(\begin{array}{l} A = \left( {15{x^5}{y^3} – 10{x^3}{y^2} + 20{x^4}{y^4) }} \right):5{x^2}{y^2}\\ = 15{x^5}{y^3}:5{x^2}{y^2} – 10{x^3} {y^2}:5{x^2}{y^2} + 20{x^4}{y^4}:5{x^2}{y^2}\\ = 3{x^3} y – 2x + 4{x^2}{y^2} \end{array}\)

Replace x=-1; y=2 in A we get

\(A = 3{\left( { – 1} \right)^3}.2 – 2\left( { – 1} \right) + 4{\left( { – 1} \right)^2}{ .2^2} = 12\)