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( a - b ) - ( a - b - c ) - ( 2b + c - a )
= a - b - a - b - c - 2b + c - a
= a - a - a - b - b - 2b - c + c
= a - 2b
\(-\left[-a-\left(-b\right)-c\right]-\left(a+b\right)+c\)
\(=a+b+c-a-b+c\)
\(\left(2x+y\right)-\left(-2x+3y\right)+y\)
\(\left(2x+y\right)+2x-3y+y\)
\(\left(a+2b+c\right)-\left(-a-2a-2c\right)-\left(4b+2a+c\right)-a-c\)
\(=a+2b+c+a+2b+2c-4b-2a-c-a-c\)
A= ( a - b) - ( a - b -c ) - ( 2a + c - a)
\(=a-b-a+b+a-2a-c+a\)
\(=\left(a-a+a+a-2a\right)+\left(-b+b\right)+c\)
\(=\left(2a-2a\right)+c\)
\(=c\)
Giải:
\(A=\left(a+b\right)-\left(a-b\right)+\left(a-c\right)-\left(a+c\right)\)
\(\Leftrightarrow A=a+b-a+b+a-c-a-c\)
\(\Leftrightarrow A=\left(a-a+a-a\right)+\left(b+b\right)+\left(-c-c\right)\)
\(\Leftrightarrow A=2b-2c\)
\(\Leftrightarrow A=2\left(b-c\right)\)
Vậy ...
a)
A = ( a+b) - (a-b) + (a-c) - (a+c)
A = a + b - a + b + a- c - a - c
A = ( a - a + a -a) + ( b + b) + ( -c - c )
= 2b -2c
$A = (a + b) - (a + b) + (a - c) - (a + c)$
$A=a+b-a-b+a-c-a-c$
$A=-2c$
A = (a - b ) - ( a - b - c) - ( 2b +c - a )
= a - b - a + b + c - 2b - c + a
= ( a - a + a) - (b - b + 2b) + ( c- c)
= a - 2b + 0
= a - 2b
A= (a - b) - (a - b - c) - (2b + c - a)
= a - b - a + b + c - 2b -c + a
= a - 2b