2 Tính:
($frac{5}{3}$ – $frac{3}{7}$+9)-( 2+$frac{5}{7}$- $frac{2}{3}$)+($frac{8}{7}$ -$frac{4}{3}$-10)
1 tìm x:
$frac{1}{x(x+1)}$ +$frac{1}{(x+1)(x+2)}$ +$frac{1}{(x+2)(x+3)}$ -$frac{1}{x}$ =$frac{x}{y}$ $frac{1}{2010}$
2 Tính: ($frac{5}{3}$ – $frac{3}{7}$+9)-( 2+$frac{5}{7}$- $frac{2}{3}$)+($frac{8}{7}$ -$frac{4}{3}$-10) 1 tìm x:
By Cora
Giải thích các bước giải:
`2. Tính : `
`(5/3 – 3/7 + 9) – (2 + 5/7 – 2/3) + (8/7 – 4/3 – 10)`
`= 5/3 – 3/7 + 9 – 2 – 5/7 + 2/3 + 8/7 – 4/3 – 10`
`= (5/3 + 2/3 – 4/3) + ( -3/7 – 5/7 + 8/7) + ( 9 – 2 – 10)`
`= 1 – 3`
`= -2`
`1, Tìm x : `
Đáp án:
Giải thích các bước giải:
( 5/3 – 3/7 + 9) – ( 2 +5/7 – 2/3) + (8/7 – 4/3 -10)
= 5/3 – 3/7 + 9 – 2 – 5/7 + 2/3 + 8/7 – 4/3 – 10
= ( 5/3 + 2/3 – 4/3) – ( 3/7 + 5/7 – 8/7) + (9-2-10)
= 1 – 0 -3
= -2
$\frac{1}{x(x+1)}$ + $\frac{1}{(x+1)(x+2)}$ + $\frac{1}{(x+2)(x+3)}$ – $\frac{1}{x}$ = $\frac{x}{y}$.$\frac{1}{2010}$
⇔ $\frac{1}{x}$ – $\frac{1}{(x+1)}$ + $\frac{1}{(x+1)}$ – $\frac{1}{(x+2)}$+$\frac{1}{(x+2)}$ – $\frac{1}{(x+3)}$ -$\frac{1}{x}$ = $\frac{x}{y}$.$\frac{1}{2010}$
⇔ 0 = $\frac{x}{y}$.$\frac{1}{2010}$
⇒ x = 0