Question

[Trần Tiến Đạt]

Bỏ ngoặc rồi rút gọn biểu thức:

 a) - ( - a + c – d ) – ( c – a + d )                 ; b) – ( a + b  - c + d ) + ( a – b – c –d )

 c)  a( b – c – d ) – a ( b + c – d )                ; d)(a+ b) ( c + d) – ( a + d ) ( b + c )

 e)( a + b ) ( c – d ) – ( a – b ) ( c + d )      ; f) ( a + b ) ² – ( a – b ) ²

Answer 1

[Phong Thần]

a) - ( - a + c – d ) – ( c – a + d ) 

= a - c - d - c + a + d

= (a + a) + (-c - c) + (-d + d)

= 2a - 2c               

b) – ( a + b  - c + d ) + ( a – b – c –d )

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

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

= -2b - 2d

Answer 2

[Tri Tran Thien]

a) - ( - a + c - d) - ( c - a + d )

= a - c + d - c + a - d 

= 2a

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

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

=-2d -2b

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

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

= ab-ac-ad-ab-ac+ad

= -2ab-2ac

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

= ac+ad+bc+bd - (ab+ac+bd+cd)

= ac+ad+bc+bd-ab-ac-bd-cd

=ad+bc-ab-cd