bai 1. 11/3.40/13+37/5:7/33-(11/13.1/3+33/7:5/2)

bai 2.tim x

a,3.(x-1)-5.(-7)=(-2)^3-2x

b,2./(1-x)^2+1/-2^2.3=8

bai 3,cho bieu thuc

M=n+1/n+1 - 3-8n/n+1 + 8/n+1

tim cac gia tri cua n de bieu thuc M co gia tri la so nguyen

bai 4,So hoc sinh cua 1 truong ko qua 1000 em,neuxeptoan bo so hoc sinh cua truong do thanh cac hang,moi hang 20 nguoi thi con thieu 5 nguoi,neu xep moi hang 25 nguoi hoac 30 nguoi thi deu thua 15 nguoi , neu xep 42 hang thi vua du . hoi truong do co bao nhieu hoc sinh

bai 5,cho bieu thuc

A=2+2^2+...+2^200

c/m rang

a, A+2 la 1 luy thua cua 2

b, Achia het cho 30

c,A co phai la so chinh phuong ko ? vi sao ?

bai 6,cho 2 bieu thuc

A=1/1+2 + 1/1+2+3 + ...1/1+2+3+...+99

B=1 + 1/2^2+1/3^2 + ...+1/49^2

c/m rang A<B

luc 6h sang mot xe tai va mot xe may cung xuat phat tu a den b van toc xe tai la 50 km/h van toc xe may la 30 km/h luc 8h sang mot xe

con cung di tu a den b voi van toc 60 km/h.

a} gia thiet rang co mot xe may thu hai cung xuat phat tu a den b cung mot luc voi xe tai va xe may thu nhat nhung di voi van toc 40 km/h hay viet bieu thuc tinh quang duong xe tai xe may thu nhat xe may thu hai di duoc sau t gio chung to rang xe may thu hai luon o vi tri chinh giua xe tai va xe may.

b} viet bieu thuc tinh quang duong xe may thu hai va xe con di duoc sau khi xe con xuat phat may gio.

c}den may gio thi xe con o chinh giua xe may thu nhat  va xe tai ?