bài 2: tính giá trị các bt sau:
a) N=\(\frac{13}{12}\times a-\frac{1}{4}\times b-\frac{13}{12}\times b\)với a-b=\(\frac{3}{8}\)
b)C=\(\frac{3}{16}\times a-\frac{3}{8}\times b+\frac{3}{16}\times c\)với a+c=2b+1
bài 3:
A= 1+\(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+.....+\frac{1}{63}\)
CMR:A<6
M= 1+\(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+....+\frac{1}{199}+\frac{1}{200}\)
CMR:M>\(2\frac{1}{12}\)
B=\(\frac{1}{^{2^2}}+\frac{1}{3^2}+\frac{1}{4^2}+....+\frac{1}{19^2}+\frac{1}{20^2}\)
CMR:B<\(\frac{3}{4}\)
C\(=\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+.....+\frac{1}{100^2}\)
CMR:C<1
