Question

Tính một cách hợp lý

(-3/4+5/13)x7/2-(9/4-8/13)x7/2

 

Answer 1

`!`

`(-3/4 + 5/13) xx 7/2 - (9/4 - 8/13 ) xx 7/2`

\(=\left[\left(-\dfrac{3}{4}+\dfrac{5}{13}\right)-\left(\dfrac{9}{4}-\dfrac{8}{13}\right)\right]\times\dfrac{7}{2}\\ =\left(-\dfrac{3}{4}+\dfrac{5}{13}-\dfrac{9}{4}+\dfrac{8}{13}\right)\times\dfrac{7}{2}\\ =\left[\left(-\dfrac{3}{4}-\dfrac{9}{4}\right)+\left(\dfrac{5}{13}+\dfrac{8}{13}\right)\right]\times\dfrac{7}{2}\\ =\left(-\dfrac{12}{4}+\dfrac{13}{13}\right)\times\dfrac{7}{2}\\ =\left(-3+1\right)\times\dfrac{7}{2}\\ =-2\times\dfrac{7}{2}\\ =-\dfrac{14}{2}\\ =-7\)