\(a)\) \(\left( {{x^2} - 1} \right)\left( {{x^2} + 2x} \right)\)\(=x^2.x^2+x^2.2x-1.x^2-1.2x\) \( = {x^4} + 2{x^3} - {x^2} - 2x\)
\(b)\) \(\left( {x + 3y} \right)\left( {{x^2} - 2xy + y} \right)\)\(=x.x^2-x.2xy+x.y+3y.x^2\)\(-3y.2xy+3y.y\)\( = {x^3} - 2{x^2}y + xy + 3{x^2}y - 6x{y^2} + 3{y^2}\)
\( = {x^3} + {x^2}y + xy - 6x{y^2} + 3{y^2}\)
\(c)\) \(\left( {2x - 1} \right)\left( {3x + 2} \right)\left( {3 - x} \right)\) \( = \left( {6{x^2} + 4x - 3x - 2} \right)\left( {3 - x} \right)\)
\( = \left( {6{x^2} + x - 2} \right)\left( {3 - x} \right) \)\(= 18{x^2} - 6{x^3} + 3x - {x^2} - 6 + 2x \)\(= 17{x^2} - 6{x^3} + 5x - 6\)
