Question

Chứng minh đẳng thức:

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

b) - (a - b - c) + (-b + c + a) - (a + b – c) = -a – b + 3c

Answer 1

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

\(b,VT=-\left(a-b-c\right)+\left(-b+c+a\right)-\left(a+b-c\right)=-a+b+c-b+c+a-a-b+c=-a-b+3c=VP\)