Question

\(\frac{-1}{1.2}+\frac{-1}{2.3}+\frac{-1}{3.4}+\frac{-1}{4.5}\)

Answer 1

=>-(1-1/2+1/2-1/3+1/3-1/4+1/4-1/5)

=>-(1-1/5)

=>-4/5

Answer 2

\(\:\frac{-1}{1.2}+\frac{-1}{2.3}+\frac{-1}{3.4}+\frac{-1}{4.5}\)

\(=-1\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}\right)\)

=\(-1\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}\right)\)

=\(-1\left(1-\frac{1}{5}\right)\)

=\(-1\times\frac{4}{5}\)

=\(\frac{-4}{5}\)