Question

5. Tính giá trị của biểu thức.

A=\(\dfrac{1}{3589}\).7\(\dfrac{1}{297}\)-3\(\dfrac{3588}{3589}\).\(\dfrac{2}{297}\)-\(\dfrac{7}{3589}\)-\(\dfrac{3}{3589.297}\)

Answer 1

Sửa lại :) bài dưới vô tình gõ sai ~

Đặt $a=\dfrac{1}{3589};b=\dfrac{1}{297}$

$=>A=a(7+b)-(4-a)2b-7a-3ab$

$=>A=7a+ab-8b+2ab-7a-3ab$

$=>A=-8b=\dfrac{-8}{297}$

Answer 2

\(A=\dfrac{1}{3589}.7\dfrac{1}{297}-3\dfrac{3588}{3589}.\dfrac{2}{297}-\dfrac{7}{3589}-\dfrac{3}{3589.297}\)

\(A=\dfrac{1}{3589}.(7+\dfrac{1}{297})-(3+1-\dfrac{1}{3589}).\dfrac{2}{297}-\dfrac{7}{3589}-\dfrac{3}{3589.297}\)

\(A=\dfrac{1}{3589}.7+\dfrac{1}{3589}.\dfrac{1}{297}-\dfrac{6}{297}-\dfrac{2}{297}+\dfrac{2}{3589.297}-\dfrac{7}{3589}-\dfrac{3}{3589.297}\)

\(A=\dfrac{7}{3589}+\dfrac{1}{3589.297}-\dfrac{8}{297}+\dfrac{2}{3589.297}-\dfrac{7}{3589}-\dfrac{3}{3589.297}\)

\(A=0-\dfrac{8}{297}\)

\(A=-\dfrac{8}{297}\)

Answer 3

Trong những bài mà có nhiều giá trị giống nhau thì tốt nhất là nên đặt ẩn nha bạn :) :v

Đặt $a=\dfrac{1}{3589};b=\dfrac{1}{297}$. Ta có :

$A=a(7+b)-(4-a)2b-7a-3ab$

$=>A=7a+ab-8b+2ab-7a-3ab$

$=>A=8b=\dfrac{8}{297}$