Question

A=1/1x4+1/7x10+......+1/97x100

Giúp mk với ai đng mk tick :)

Answer 1

\(A=\frac{1}{1.4}+\frac{1}{4.7}+.....+\frac{1}{97.100}\)

\(3A=\frac{3}{1.4}+\frac{3}{4.7}+......+\frac{3}{97.100}\)

\(3A=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+.......+\frac{1}{97}-\frac{1}{100}\)

\(3A=1-\frac{1}{100}\)

\(3A=\frac{99}{100}\)

\(A=\frac{99}{100}:3\)

\(A=\frac{33}{100}\)

Answer 2

A=1/1x4+1/4x7+.....+1/97x100

A=1x3/1x4x3+1x3/4x7x3+....+1x3/97x100x3

A=1/3x(3/1x4+3/4x7+...+3/97x100)

A=1/3x(1-1/4+1/4-1/7+.....+1/97-1/100)

A=1/3x(1-1/100)

A=1/3x99/100

A=33/100