a) (-8)+10+(-12)+14+...+(-32)+34+(-36)+38
=(-8+10)+(-12+14)+...+(-32+34)+(-36+38)
=2+2+...+2+2 ( Có 16 số 2)
=2.16
=32
Trả lời:
\(a)\)\(\left(-8\right)+10+\left(-12\right)+14+...+\left(-32\right)+34+\left(-36\right)+38\)(Có 16 số)
\(=\left[\left(-8\right)+10\right]+\left[\left(-12\right)+14\right]+...+\left[\left(-36\right)+38\right]\)(Có 8 nhóm)
\(=\left(-2\right)+\left(-2\right)+...+\left(-2\right)\)
\(=\left(-2\right).8\)
\(=-16\)
\(b,\)\(1+3+5+...+49-2-4-6-...-50\)
\(=\left(1-2\right)+\left(3-4\right)+...+\left(49-50\right)\)(Có 25 nhóm)
\(=\left(-1\right)+\left(-1\right)+...+\left(-1\right)\)
\(=\left(-1\right).25\)
\(=-25\)
Hok tốt!
Good girl
