KHAI TRIEN VE TRAI

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

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

=ad+bc-ab-cd

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

=(a-c)(-b+d) GIONG NHU VE PHAI

THAY DUNG THI

a, Có : a.(b-c)+c.(a-b) = ab-ac+ac-bc = ab-bc = b.(a-c)

b, Có : (a+b).(c+d)-(a+d).(b+c) = ac+bc+ad+bd-ab-bd-ac-cd = ad+bc-ab-cd 

= (ad-cd)-(ab-bc) = d.(a-c)-b.(a-c) = (a-c).(d-b)

Tk mk nha

a, Có : a.(b-c)+c.(a-b) = ab-ac+ac-bc = ab-bc = b.(a-c)
b, Có : (a+b).(c+d)-(a+d).(b+c) = ac+bc+ad+bd-ab-bd-ac-cd = ad+bc-ab-cd 
= (ad-cd)-(ab-bc) = d.(a-c)-b.(a-c) = (a-c).(d-b)

tk cho mk nha $_$

VT = a ( b + c ) − b ( a − c ) = ab + ac − ba + bc = ( ab − ab ) + ( ac + bc ) = 0 + a + b . c = VP Vậy   a ( b + c ) − b ( a − c ) = ( a + b ) . c

VT = a ( b + c ) − b ( a − c ) = ab + ac − ba − bc    = ab + ac − ba + bc = ac + bc = c ( a + b ) = VP   ( dpcm )

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

\(=ab+ac-\left(ab-bc\right)\)

\(=ab+ac-ab+bc\)

\(=ac+bc\)

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

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

\(=\left(aa+ab\right)-\left(ab+bb\right)\)

\(=aa+ab-ab-bb\)

\(=aa-bb\)

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

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

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

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

=0+(a+b).c=(a+b).c(đpcm)

Ta có a .(b + c) - b .(a +c)

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

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

=0 + (a + b) . c

= (a +b) . c

Biến đổi vế trái ta có :

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

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

= a.c + b. c = ( a.b ) + c 

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

ab - ac + ca - cb - ba + cb = 0

(ab - ab) - (bc - bc) - (ac - ac) =0

0 - 0 -0 = 0 (đpcm)

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

= ab - ac + ca - cb

= ab - cb

= b(a-c) 

Hok tốt !