Giup minh giai bai toan nay voi
Khong thuc hien phep tinh xet xem tich sau co tan cung bang chu so nao
a.2*12*22*32*...*2012
b.3*13*23*...*2013
c.4*14*24*...*2004
d.2*12*22*...*2020
Cac ban giai ro giup minh nha.Minh cam on

1)trong mot phepnhan co thua so thu hai la 64, khi thuc hien phep nhan, ban Minh da viet cac tich rieng thang cot voi nbhau nen ket qua tim duoc la 870. tim tich dung cua phep nhan

2 ) Khi thuc hien phep nhan 983 voi 1 so co 3 chu so , ban binh da dat tich rieng thu 2 thang cot voi tich rieng thu 3 nen duoc ket qua la 70776 . Em hay tim thua so co 3 chu so chua biet trong phep nhan tren , biet chu so hang tram hon chu so hang chuc 1 don vi

Cho A = 1/5 + 1/6 + 1/7 + 1/8 + 1/9.

Khong thuc hien phep ting , hay so sanh gia tri cua A voi1

khong thuc hien phep tinh hay cho biet tich sau co chu so tan cung la chu so nao

                                             2*12*22*32*...........*202*212

khong gia tri xet xem cac tong sau day co chia het cho 9 hay khong 2*3*4*5*6*7+8*9*10*11*12

bai 1;tinh gia tri bieu thuc 17a+15b+6a+8b voi a+b =100

bai 2;tich cua 2 so la 6210.neu giam 1 thua so di 7 don vi thi tich moi la 5265.tim cac thua so  cua tich

bai 3;co 5 so tu nhien nao ma tich cua chung bang1001 va chu so tan cung la 6

bai 4;tinh;333...3.999...9 trong do co 50 chu so 3 va 50 chu so 9

a)Khong thuc hien phep tinh xet xem tong sau co chia het cho 9 khong?   A=270+3105+150; B=504+1378+612

b)Phan tich cac so ra thua so nguyen to:36;98;39;72

thuc hien cac phep tinh sau ;

2va3/4 . (-0,4)+ 1va3/5 . 1,75 + (-7,2) : 9 / 11

1/8 . 15va2/5 + 1va4/5 . 7/8 - 17va 1/5 . 1/8 

-5/7 . 2/11 + (-5) / 7 . 9/11 + 1va5/7

6/5 + 5/8 : 5 - 3/16 . (-2)³

^{Co 1 ban thuc hien phep nhan 2015 voi STN A da quen viet chu so 0 cua 2015 nen tich giam di 154800. Hay tim tich dung.}