Question

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

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

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

Mọi người chứng minh cho tui 

Answer 1

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

                               = -b ( đpcm)

2/ Sủa đề : (a + b ) - (b - a ) +c = 2a + c

a + b - b + a + c= 2a + c( đpcm)

3/ a(b + c ) -a(b + d ) = a[ (b + c )- ( b+ d) ]

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

                                 = a(c -d) ( đpcm)

hok tốt!!

Answer 2

(a - b + c) - (a + c) = -b                                                                                                                                                             a - b + c - a - c = -b a + (-b) + c + (-a) + (-c) = -b [a + (-a)] + [c + (-c)] + (-b) = -b0 + 0 + (-b) = -b-b = -b  

Answer 3

(a + b) - (b - a) + c = 2a + c a + b - b + a + c = 2a + ca + b + (-b) + a + c = 2a + c(a + a) + [ b + (-b)] + c = 2a + c2a + 0 + c = 2a + c 2a + c = 2a + c 

Answer 4

a(b + c) - a(b + d) = a(c - d)a(b + c - b - d) = a(c - d)a[(b - b) + (c - d)] = a(c - d)a[0 + (c - d)] = a(c - d) a(c - d) = a(c - d) 

Answer 5

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

\(a-b+c-a-c=-b\Leftrightarrow-b=-b\left(đpcm\right)\)

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

\(a+b-b+a+c=2a+c\Leftrightarrow2a+c=2a+c\left(đpcm\right)\)

\(a\left(b+c\right)-a\left(b+d\right)=a\left(c-d\right)\)

\(ab+ac-ab-ad=ac-ad\Leftrightarrow ac-ad=ac-ad\left(đpcm\right)\)