1/ (a - b +c ) - (a + c ) = a - b + c - a -c
= -b ( đpcm)
2/ Sủa đề : (a + b ) - (b - a ) +c = 2a + c
a + b - b + a + c= 2a + c( đpcm)
3/ a(b + c ) -a(b + d ) = a[ (b + c )- ( b+ d) ]
= a .( b+ c - b - d )
= a(c -d) ( đpcm)
hok tốt!!
\(\left(a-b+c\right)-\left(a+c\right)=-b\)
\(a-b+c-a-c=-b\Leftrightarrow-b=-b\left(đpcm\right)\)
\(\left(a+b\right)-\left(b-a\right)+c=2a+c\)
\(a+b-b+a+c=2a+c\Leftrightarrow2a+c=2a+c\left(đpcm\right)\)
\(a\left(b+c\right)-a\left(b+d\right)=a\left(c-d\right)\)
\(ab+ac-ab-ad=ac-ad\Leftrightarrow ac-ad=ac-ad\left(đpcm\right)\)