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efectuati (3×+7×-12×)-(15×-21×)




Răspuns :

(3x+7x-12x)-(15x-21x)=
=-2x-(-6x)=
=-2x+6x=
=4x
(3x+7x-12x)-(15x-21x)=

=(10x-12x)-(-6x)=

=(-2x)-(-6x)=

= -2x +6x=

= 4x