Va rog la A-B pun termini in paranteze schimb semnele sau nu ???

[tex] A-B = a^2+x+2-(3a^2+2x-7) \\ \\
A-B = a^2+x+2-3a^2-2x+7 \\ \\
\to \boxed{A-B = -2a^2-x+9} [/tex]

a) A + B = a² + x + 2 + 3 a ² + 2 x - 7 = 4 a² + 3 x - 5

b) A - B = ( a² + x + 2) - ( 3 a² + 2 x - 7 ) = a² + x + 2 - 3 a² - 2 x + 7 = - 2 a² - x + 9

= 9 - x - 2 a²

c) A + B + C = a² + x + 2 + 3 a ² + 2 x - 7 + 4 x + 12 =

= ( a² + 3 a² ) + ( x + 2 x + 4 x ) + ( 2 - 7 + 12 ) =

= 4 a² + 7 x + 7