Đáp án:
Giải thích các bước giải:
M=6^2 +8^2 +10^2 +...+102^2
=6. 8 -2.6 +8.10 -2.8 +10.12-2.10 +...+102.104 - 2.102
=(6.8+8.10+10.12+...+102.104)-2.( 6+8+10+...+102)
=A -2.B
Ta có A= 6.8+8.10+10.12+...+102.104
=> A+2.4 +4.6 = 2.4+4.6 +6.8+8.10+10.12+...+102.104
=> A+32 =2.4+4.6 +6.8+8.10+10.12+...+102.104
=> 6 (A+32)=2.4.6+4.6.6+6.8.6+...+102.104.6
=> 6(A+32)=2.4.6 +4.6.8-2.4.6+6.8.10- 4.6.8 +...+102.104.106- 100.102.104
=> 6(A+32)=102.104.106=1124448
=>A+32=187408
=>A=187376
Lại có: B=6+8+10+...+102
=(6+102) *49/2
=2646
=>M= 187376 + 2. 2646=192668
