Question

Tính giá trị biểu thức

\(A=\left(\dfrac{ab}{2}-\dfrac{6ab}{7}\right):\dfrac{5b^2}{14}biết;a=\dfrac{2007}{2010},b=\dfrac{2015}{2016}\)

Answer 1

\(A=\left(\dfrac{ab}{2}-\dfrac{6ab}{7}\right):\dfrac{5b^2}{14}=-\dfrac{5ab}{14}:\dfrac{5b^2}{14}=-\dfrac{5ab}{14}\cdot\dfrac{14}{5b^2}=-\dfrac{a}{b}\)

Thay \(a=\dfrac{2007}{2010};b=\dfrac{2015}{2016}\) vào A ta có:

\(A=-\dfrac{a}{b}=-\dfrac{\dfrac{2007}{2010}}{\dfrac{2015}{2016}}=-\dfrac{2007}{2010}\cdot\dfrac{2016}{2015}=-\dfrac{4046112}{4050150}\approx-1\)

Vậy \(A\approx-1\) tại \(a=\dfrac{2007}{2010};b=\dfrac{2015}{2016}\)

Answer 2

Dấu \(\approx\) có nghĩa là gần bằng