\(\frac{1}{35}+\frac{1}{63}+\frac{1}{99}+\frac{1}{143}\)=\(\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}+\frac{1}{11.13}\)

=\(\frac{1}{2}.\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+\frac{1}{11}-\frac{1}{13}\right)\)

=\(\frac{1}{2}.\left(\frac{1}{5}-\frac{1}{13}\right)=\frac{1}{2}.\frac{8}{65}=\frac{4}{65}\)

x²y + 0,5xy³ - 7,5x³y² + x³ + 3xyz² - x²y + 5,5x³y²

= 0,5xy³ -2x³y² + x³+ 3xyz²

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