GIÚP MK NHA

4 câu trả lời
Toán lớp 6 Đại số lớp 6



 

C=115+135+...+12499C=115+135+...+12499

=13.5+15.7+...+149.51=13.5+15.7+...+149.51

=12(23.5+25.7+...+249.51)=12(23.5+25.7+...+249.51)

=12(13−15+15−17+...+149−151)=12(13−15+15−17+...+149−151)

=12(13−151)=12(13−151)

=12.1651=851=12.1651=851

Vậy C=8/51

 

 

= 1-1/46
=45/46

a.1/1.2 + 1/2.3 + ... + 1/49.50
= 2-1/1.2 + 3-2/2.3 + ... + 50-49/49.50
= 2/1.2 - 1/1.2 + 3/2.3 - 2/2.3 + ... + 50/49.50 - 49/49.50
= 1 - 1/2 + 1/2 - 1/3 + ... + 1/49 - 1/50
= 1 - 1/50 = 49/50
b.3/1.4 + 3/4.7 +3/7.10 + ... + 3/40.43 + 3/43.46
= 4-1/1.4 + 7-4/4.7 +10-7/7.10 + ... + 43-40/40.43 + 46-43/43.46
= 4/1.4 - 1/1.4 + 7/4.7 - 4/4.7 + 10/7.10 - 7/7.10 + ... + 43/40.43 - 40/40.43 + 46/43.46 - 43/43.46
= 1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + ... + 1/40 - 1/43 + 1/43 - 1/46
= 1 - 1/46 = 45/46
c.1/15 + 1/35 + ... + 1/2499
= 2(1/15 + 1/35 + ... + 1/2499) : 2
= (2/3.5 + 2/5.7 + ... + 2/49.51) : 2
= (5-3/3.5 + 7-5/5.7 + ... + 51-49/49.51) : 2
= (5/3.5 - 3/3.5 + 7/5.7 - 5/5.7 + ... + 51/49.51 - 49/49.51) : 2
= (1/3 - 1/5 + 1/5 - 1/7 + ... + 1/49 - 1/51) : 2
= (1/3 - 1/51) : 2
= 16/51 : 2
= 8/51