Question

помогите пожалуйсто 249

Answer 1

1) x+y+x-y= 2x
x+y - (x-y)= 2y
2) x^2 - y^2 + x^2 + y^2=2x^2
x^2 - y^2 - ( x^2 + y^2) = -2y^2
3)a^2 - a +4 - a^2 - a - 4= -2a
a^2 - a +4 -(- a^2 - a - 4) =2a^2 + 8
4) b^3- 8 - b^3 - 8 = -16
 b^3- 8 - ( - b^3 - 8) =2b^3