$A=1.2.3+2.3.4+…+90.91$ Question $A=1.2.3+2.3.4+…+90.91$ in progress 0 Môn Toán Amity 4 years 2020-10-17T23:24:04+00:00 2020-10-17T23:24:04+00:00 1 Answers 79 views 0
Answers ( )
`A=1.2.3+2.3.4+…………+90.91.92`
`4A=1.2.3.4+2.3.4.4+…………+90.91.92.4`
`4A=1.2.3.4+2.3.4.5-1.2.3.4+3.4.5.6-2.3.4.5+………….+90.91.92.93-89.90.91.92`
`4A=90.91.92.93`
`A=(90.91.92.93)/4=17518410`