Question

Решите пожайлуста 14 номер

Answer 1

$69\cdot 71=(70-1)(70+1)=70^2-1^2=4900-1=4899\\\\58\cdot 62=(60-2)(60+2)=60^2-2^2=360-4=3596\\\\10 \frac{1}{7}\cdot 9\frac{6}{7}=(10+ \frac{1}{7} )(10-\frac{1}{7}) =10^2-( \frac{1}{7} )^2=100-\frac{1}{49}=\\\\=\frac{4899}{49}=99\frac{48}{49}$