Question

\(A=1.4+4.7+7.10+.....+91.94=?\)

Answer 1

9A = 1.4.[7+2] + 4.7. [10-1] + 7.10.[13-4] +...+ 91.94. [97-88]

= 1.4.7 + 1.2.4 + 4.7.10 - 1.4.7 + 7.10.13 - 4.7.10+...+ 91.94.97 - 88.91.94

= 1.2.4 + 91.94.97 = 8 +829738 = 829746 => A = 829746 : 9 = 92194

đúng cái nhé

Answer 2

9A = 1.4.[7+2] + 4.7. [10-1] + 7.10.[13-4] +...+ 91.94. [97-88]

= 1.4.7 + 1.2.4 + 4.7.10 - 1.4.7 + 7.10.13 - 4.7.10+...+ 91.94.97 - 88.91.94

= 1.2.4 + 91.94.97 = 8 +829738 = 829746 => A = 829746 : 9 = 92194

đúng cái nhé