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B1:
a, a+b+(-a)+b+a+(-c)+(-a)+(-c)=[a+(-a)+a+(-a)]+(b+b)+[(-c)+(-c)]=0+2.b+(-2).c
b, a+b+(-c)+a+(-b)+c+(-b)+(-c)+a+(-a)+b+c=[a+a+a+(-a)]+[b+(-b)+(-b)+b]+[(-c)+c+(-c)+c]=2.a+0+0=2a
B2:
N=(a+b)-(a-b)+(a+b)=a+b+(-a)+b+a+b=[a+(-a)+a)+(b+b+b)=a+3.b
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rút gọn biểu thức
a,A=(a-b)-(a-b+c)
b,B=-(a+b+c)-(a+b-5)
\(\left(a+b-c\right)+\left(b+c-a\right)+\left(a+c-b\right)\)
\(=a+b-c+b+c-a+a+c-b\)
\(=a+b-c\)
( a - b ) + ( b - c + a ) + ( c - b )
= a - b + b - c + a + c - b
= 2a - b
\(\left(a+b-c\right)+\left(a-b+c\right)-\left(a-b-c\right)\)
\(=a+b-c+a-b+c-a+b+c\)
\(=a+b+c\)
( a + b - c ) + ( a - b + c ) - ( a - b - c )
= a + b + c + a - b + c - a + b + c
= a + b + 3c
Thu gọn biểu thức sau :
a) a - b + c - (a - b + c) + 3b
b) - (2a - b) - (b + 3a)
c) a(b + c) - b(a - c)
a) a - b + c - (a - b + c) + 3b
= a - b + c - a + b - c +3b
= 3b
b) - (2a - b) - (b + 3a)
= -2a + b - b - 3a
= -5a
c) a(b + c) - b(a - c)
= ab + ac - ab + bc
= ac + bc
\(a,a-b+c-\left(a-b+c\right)+3b=a-b+c-a+b-c+3b\)
\(=3b\)
\(b,-\left(2a-b\right)-\left(b+3a\right)=-2a+b-b-3a=-5a\)
\(c,a\left(b+c\right)-b\left(a-c\right)=ab+ac-ab+bc=ac+bc\)
a, (a+b)-(a-b)+(a-c)-(a+c)=[(a+b)-(b+a)]+[(a+c)-(c+a)]=0+0=0
a) ( a + b + c ) - ( a - b - c )
= ( a + b + c ) - a + b + c
= a + ( - a ) + b + c + b + c
= 0 + b + c + b + c
= ( b + c ) x 2
b) ( a + b - c ) + ( a - b ) - ( a - b - c )
= ( a + b - c ) + a - b - a + b + c
= [ a + a + ( -a ) ] + [ b + ( -b ) + b ] + [ ( -c ) + c ]
= a + b + 0
= a + b
c) - ( a - b - c ) + ( -a + b - c ) - ( -a + b + c )
= ( -a ) + b + c + ( -a ) + b - c + a - b - c
= [ ( -a ) + ( -a ) + a ] + [ b + b + ( -b ) ] + [ c + ( -c ) + ( -c ) ]
= ( -a ) + b + ( -c )
a , ( a + b + c ) - ( a - b - c )
= a + b + c - a + b + c
= ( a - a ) b + b + c + c
= 0 + b + b + c + c
= 0 + 2b + 2c
= 0 + 2(b + c )
= 2(b+c)
b , ( a + b - c ) + ( a - b ) - ( a - b - c )
= a + b - c + a - b - a + b + c
= ( a - a ) + b + b + ( - c + c )
= 0 + b + b + 0
= 2b
c , - ( a - b - c ) + ( - a + b - c ) - ( - a + b + c )
= - a + b + c - a + b - c + a - b - c
= ( - a + a ) + ( b - b ) + ( c - c ) + a + b
= 0 + 0 + 0 + a + b= a + b
a) (a+b) - (a-b) + (a-c) - (a+c)
=a+b-a+b+a-c-a-c
=2b-2c
b) (a+b-c) + (a-b+c) - (b+c-a) - (a-b-c)
=a+b-c+a-b+c-b-c+a-a+b+c
=2a
a) (a+b)-(a-b)+(a-c)-(a+c)=a+b+a+b+a-c+a-c=(a+a+a+a)+(b+b)+(-c-c)=4a+2b+2*-c
b) (a+b-c)+(a-b+c)-(b+c-a)-(a-b-c)=a+b-c+a-b+c+b-c+a+a+b+c=(a+a+a+a)+(b-b+b+b)+(-c+-c+c)
=4a+2b+ -c
a,(a+b)-(a-b)+(a-c)-(a+c)
=a+b-a+b+a-c-a-c
=2b+2(-c)
b,(a+b-c)+(a-b+c)-(b+c-a)-(a-b-c)
=a+b-c+a-b+c-b-c+a-a+b+c
=2a
B = ( a+ b – c ) + ( a – b ) – ( a – b - c )
= a+ b – c + a – b – a + b + c = a + b