用简便方法计算1+2+3+4+······+97顺便帮我用简便方法计算2+4+6+······+100
1+2+3+4+······+97
=(1+97)×97÷2
=98×97÷2
=49×97
=4753
2+4+6+······+100
=(2+100)×50÷2
=102×25
=2550