2/(11x13) = 1/11 - 1/13 ; 2/(13x15) = 1/13 - 1/15 ; 2/(15x17) = 1/15 - 1/17 ; 2/(17x19) = 1/17 - 1/19 ; 2/(19x21) = 1/19 - 1/21

2/(11x13) + 2/(13x15) + 2/(15x17) + 2/(17x19) 2/(19x21) =

1/11 - 1/13 + 1/13 - 1/15 + 1/15 - 1/17 + 1/17 - 1/19 + 1/19 - 1/21 = 1/11 - 1/21 = 101231

Hay:   10/231 x 462 - X = 19

20 - X = 19

X = 20 - 19

X = 1,đó là phần b

3/5x+2/3x=-76 <=> 19/15x=-76 <=> x=-60,đó là phần a

\(a) (x-6).(-3x+15)=0\)

\(\Rightarrow x-6=0\) và \((-3x+15) =0\)

\(\Rightarrow x=6\) và \(-3x = -15\)

\(\Rightarrow x=6\) và \(x=5\)

\(60\%x+\dfrac{2}{3}x=-76\)

\(\Leftrightarrow\dfrac{3}{5}x+\dfrac{2}{3}x=-76\)

\(\Leftrightarrow\dfrac{19}{15}x=-76\)

\(\Leftrightarrow x=\dfrac{-76}{\dfrac{19}{15}}\)

\(\Leftrightarrow x=-60\)

\(60\%.x+\dfrac{2}{3}.x=-76\\ \dfrac{3}{5}.x+\dfrac{2}{3}.x=-76\\ \dfrac{19}{15}.x=-76\\ x=-76:\dfrac{19}{15}\\ x=-60.\)

\(60\%x+\dfrac{2}{3}x=-76\)

\(\dfrac{3}{5}x+\dfrac{2}{3}x=-76\)

\(x\left(\dfrac{3}{5}+\dfrac{2}{3}\right)=-76\)

\(x\dfrac{19}{15}=-76\)

\(x=-76:\dfrac{19}{15}\)

\(x=-60\)

\(60\%x+\dfrac{2}{3}x=-76\)

\(\dfrac{3}{5}x+\dfrac{2}{3}x=-76\)

\(x.\left(\dfrac{3}{5}+\dfrac{2}{3}\right)=-76\)

\(x.\dfrac{19}{15}=-76\)

\(x=-76:\dfrac{19}{15}\)

\(x=-76.\dfrac{15}{19}\)

\(x=-60\)

\(\frac{x-96}{2}+\frac{x-88}{4}+\frac{x-76}{6}+\frac{x-60}{8}=14\)

\(\frac{x-96}{2}-2+\frac{x-88}{4}-3+\frac{x-76}{6}-4+\frac{x-60}{8}-5=0\)

\(\frac{x-96}{2}-\frac{4}{2}+\frac{x-88}{4}-\frac{12}{4}+\frac{x-76}{6}-\frac{24}{6}+\frac{x-60}{8}-\frac{40}{8}=0\)

\(\frac{x-96-4}{2}+\frac{x-88-12}{4}+\frac{x-76-24}{6}+\frac{x-60-40}{8}=0\)

\(\frac{x-100}{2}+\frac{x-100}{4}+\frac{x-100}{6}+\frac{x-100}{8}=0\)

\((x-100)\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}+\frac{1}{8}\right)=0\)

\(\Rightarrow x-100=0\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}+\frac{1}{8}>0\right)\)

\(\Rightarrow x=100\)

5 + (

Mk nhan nham

imagine: Bạn dùng chỗ chữ M ngược ở phía trên đó, rồi viết lại đề nhé! Chứ viết vậy thì ra nhiểu kiểu đề lắm!

#Học tốt!

Bài 2: 

a: =>x-1=1 hoặc x-1=-1

=>x=2 hoặc x=0

b: =>x+1=-1

hay x=-2

c: =>(135-7x):9=8

=>135-7x=72

=>7x=63

hay x=9

d: =>(x+7)(x-3)<0

=>-7<x<3

e: \(\Leftrightarrow3^{x-3}=18+9=27\)

=>x-3=3

hay x=6

f: =>4-2x=0

hay x=2

bài 1 ik