(a - b - c + d) - (-a - b + c + d)
= a - b - c + d + a + b - c - d
= (a + a) + (b - b) - (c + c) + (d - d)
= 2a + 0 - 2c + 0
= 2a - 2c
= 2(a - c)
(a - b - c + d) - (-a - b + c + d)
= a - b - c + d + a + b - c - d
= 2a - 2c
= 2.(a - c) (đpcm)
Chúc em học tốt!!!
\(\left(a-b-c+d\right)-\left(-a-b+c+d\right)\) d
=a-b-c+d+a+b+c-d
=(a+a)-(b-b)-(c+c)+(d-d)
=2a-0-2c+0
=2a-2c
=2(a-c)
(a-b-c+d)-(-a-b+c+d)
=a-b-c+d+a+b-c-d
=(a+a)+(-b+b)-(c+c)+(d-d)
=2a-2c
=2(a-c) (cccm)