chứng tỏ
( a - b + c ) - ( a+ c ) = - b
( a + b ) - ( b - a ) + c = 2a + c
- ( a + b - c ) + ( a - b - c ) = - 2b
a( b + c ) - a(b + d ) = a ( c - d )
a ( b - c ) + a ( d + c ) = a ( b + d)
GIÚP MIK NHA MIK TICK CHO BN NÀO LÀM ĐÚNG
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(a - b + c) - (a + c) = a - b + c - a - c = -b (đpcm)
(a + b) - (b - a) + c = a + b - b + a + c = 2a + c (đpcm)
-(a + b - c) + (a - b - c) = -a - b + c + a - b - c = -2b (đpcm)
a.(b + c) - a.(b + d) = a.(b + c - b - d) = a.(c - d) (đpcm)
a.(b - c) + a.(d + c) = a.(b - c + d + c) = a.(b + d) (đpcm)