Question

Rút gọn biểu thức :

A=(b-c+6)-(7-a+b)+c

B=a+b-5+(-b-c+1)+c

C=2(a+b-c)-(2a+b-c-19)-2b+23

Answer 1

A = (b - c + 6) - (7 - a + b) + c

A = b - c + 6 - 7 + a - b + c

A = (b - b) + (c - c) + a + 6 - 7

A = 0 + 0 + a + (-1)

A = a + (-1)

B = a + b - 5 + (-b - c + 1) + c

B = a + b - 5 + (-b) - c + 1 + c

B = (b - b) + (c - c) + a - 5 + 1

B = 0 + 0 + a - 4

B = a - 4

C = 2(a + b - c) - (2a + b - c - 19) - 2b + 23

C = 2(a + b - c) - 2a - b + c + 19 - 2b + 23

C = 2a + 2b - 2c - 2a - b + c + 19 - 2b + 23

C = (2a - 2a) + (2b - 2b) - 2c + c - b + 19 + 23

C = 0 + 0 - 2c + c - b + 42

C = 42 - 2c + c - b

C = 42 + (-2)c + c - b

C = 42 + c(-2 + 1) - b

C = 42 + c . (-1) - b

C = 42 + (-c) - b