Question

1. Bỏ dấu 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+d) × (b+c)

d, a×(b-c-d) - a×(b+c-d)

Answer 1

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

= -2b-2d

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

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

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

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

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

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

= (b-d)(c-a)

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

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

= a[b-c-d-b-c+d]

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

= -2ca

Chúc bạn học tốt.....