= ( -a ) -b +c + a +b +c

=[ ( -a ) + a ] + b - b + c + c

= 0 + ( b-b ) + ( c+c )

=0+0+  2x

=2x

(-a-b+c)-(-a-b-c)=-a-b+c+a+b+c=2c

(-a-b+c) - (-a-b-c)

=-a-b+c+a+b+c

=(a-a)+(b-b)+(c+c)

=0+0+c.2

=c2

= -a - b + c + a + b +c -2b

= 2c- 2b

=2. ( c - b)

hok tốt

\(\left(-a-b+c\right)-\left(-a-b-c\right)-2b\)

\(=-a-b+c+a+b+c-2b\)

\(=2c-2b=2.\left(c-b\right)\)

 =   -a - b + c +a + b + c -2b

= 2c - 2b

= 2.(c - b)

hok tốt

=-a    -    b    +    c     +    a    +    b   +    c   -     2b

=2c    -    2b

=2    .     (   c   -   b)

học tốt nha bạn hiền

A = (-a - b + c) - (-a - b - c)

= -a - b + c + a + b + c

= (a - a) + (b - b) + (c + c)

= 0 + 0 + 2c

= 2c

A = (-a - b + c ) - ( -a - b - c )

A = -a -b - c + a + b + c

A = (-a + a ) + (-b + b ) + (c + c)

A= 0 + 0 + 2c

A= 2c

Vay A= 2c

tik nha

A = (-a-b+c)-(-a-b-c)

   = -a-b+c+a+b+c

   = (-a+a)-(b-b)+(c+c)

   = 0-0+c.2

   = c.2

Dùng hằng đẳng thức A² + 2AB + B² = ( A + B)² :

Ta được ... = (a-b+c+b-c)² = a²

a) \(\left(a+b\right)\left(a+b\right)\)

\(=\left(a+b\right).a+\left(a+b\right).b\)

\(=a^2+ab+ab+b^2\)

\(=a^2+2ab+b^2\)

b) \(\left(a-b\right)\left(a-b\right)\)

\(=\left(a-b\right).a-\left(a-b\right).b\)

\(=a^2-ab-ab+b^2\)

\(=a^2-2ab+b^2\)

\(\left(a+b-c\right)^2-\left(a-c\right)^2-2ab+2bc\)

\(=\left(a-c\right)^2+2b\left(a-c\right)+b^2-\left(a-c\right)^2-2ab+2bc\)

\(=2b\left(a-c\right)+b^2-2ab+2bc\)

\(=2ab-2bc+b^2-2ab+2bc=b^2\)