=(4X+4Y)*2Y

=8XY+8Y^2，

When X= 1/3 and Y=- 1/2,

Original formula =8Y(X+Y)

=8×(- 1/2)×( 1/3- 1/2)

=-4×(- 1/6)

=2/3。

7、a^2+b^2=(a+b)^2-2ab=25-6= 19.

Check the textbook, the title of question 4 is wrong.

Original formula = (2x+3y) 2-* (2x+y) (2x-y)

=4x^2+ 12xy+9y^2-(4x^2-y^2)

= 12XY+ 10Y^2

When X+ 1/3 and Y=- 1/2,

The original formula =12×1/3× (-1/2)+10× (-1/2) 2.

=-2+5/2

= 1/2。