Bài 5
\(a,357-1284+1280-1357=\left(357-1357\right)+\left(1280-1284\right)=\left(-1000\right)+\left(-4\right)=-1004\)
b, ko nhìn rõ
\(1-4-7+10+13-16-19+22-25+28+31-34+37=\left(1-4\right)-\left(7-10\right)+\left(13-16\right)-\left(19-22\right)-\left(25-28\right)+\left(31-34\right)+37=\left(-3\right)-\left(-3\right)+\left(-3\right)-\left(-3\right)-\left(-3\right)+\left(-3\right)+37=0+37=37\)