(a+b).(a+b)=(a+b)²

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

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

\(=\left(a+b\right)^2\)

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

I a I - a

= a - a

=0

TH1:|a|=a

=> |a|-a=a-a=0

TH2:|a|=-a

=> |a|-a=(-a)-a=-2a

  | a | - a

= a - a = 0

= ( -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

2ax^2-a(1+2x^2)-[a-x(x+a)]

=2ax²-2ax²+a+x²-ax+a

=(2ax²-2ax²)-(a+a)+ax+x²

=0-2a+ax+x²

=x²+ax-2a