Question

4.6x^{2}y-2.2xy+7y^{2}-(7.8xy-3.4x^{2}y+7y^{2})

x=2    y=5

Answer 1

$6x^2y-2.2xy+7y^2-(7.8xy-3.4x^2y+7y^2)=\ =6x^2y-2.2xy+7y^2-7.8xy+3.4x^2y-7y^2=\ =9.4x^2y-10xy = 10xy(0.94x -1) = \ =10 * 2 * 5(0.94 * 2 +1) = 100 * 2.88 = 288$