• a=2
• Vì (-6x2+4):(3x2+2)
• = (-12+4):(6+2) 
• = -8:8
• = -1 là số nguyên nên a=2
• Giữ đúng lời hứa là kick cho mình nhé!
• Chúc bạn học tốt!
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1/4+2/5+6/8+2/15+6/7

=(1/4+6/8)+(2/5+2/15)+6/7

=(2/8+6/8)+(6/15+2/15)+6/7

=1+8/15+6/7

=1+56/105+90/105

=1+146/105

=1+105/105+41/105

=1+1+41/105

=2+41/105

=2 và 41/105

2 và 41/105 là hỗn số nha

1/4+2/5+6/8+2/15+6/7

Ta có:

1/4=1-3/4

6/8=3/4

2/15=2/3*5=1/3-1/5

==> 1-3/4+2/5+3/4+1/3-1/5+6/7 

=1+1/3+1/5+6/7

=(105+35+21+90)/105

=251/105.

\(2x^2-10x+5=2x\left(x-5\right)+5⋮x-5\Rightarrow5⋮x-5\)

\(\Rightarrow x-5\inƯ\left(5\right)=\left\{-1;1;-5;5\right\}\Rightarrow x\in\left\{0;4;6;10\right\}\)

\(3+3^2+.....+3^{99}\)

\(=\left(3+3^2+3^3\right)+\left(3^4+3^5+3^6\right)+...+\left(3^{97}+3^{98}+3^{99}\right)\)

\(=39+3^3\left(3+3^2+3^3\right)+........+3^{96}\left(3+3^2+3^3\right)\)

\(=39+3^3\cdot39+...+3^{96}\cdot39\)

\(=39\left(1+3^3+....+3^{96}\right)\)

Vì \(39⋮13\Rightarrow39\in B\left(13\right)\)

B(13) là sao bạn

2017²⁰¹⁸ >2018²⁰¹⁷

^{k mình nha}

bạn lên hvn mà hỏi

ta co:(x^2-x+2) chia het cho (x-1)

suy ra :x*(x-1)+2 chia het cho (x-1)

ma x*(x-1) chia het cho (x-1)

suy ra 2 chia het cho (x-1)

suy ra (x-1) thuoc uoc cua 2=ngoac nhon 1,2 ngoac nhon

suy ra x thuoc 2 va3

\(x^2-x+2=x\left(x-1\right)+2⋮x-1\text{ do đó: }2⋮x-1\text{ nên: }x-1\inƯ\left(2\right)\)

nên x-1 thuộc: -1;1;-2;2 nên: x thuộc 0;2;-1;3

a) 2,63=\(2\frac{63}{100}\)

b)\(\frac{2013}{100}\)=\(20\frac{13}{100}\)=20,13

c)\(\frac{-2}{5}=\frac{-14}{35}\)

\(\frac{-3}{7}=\frac{-15}{35}\)

vì\(\frac{-14}{35}>\frac{-15}{35}\Rightarrow\frac{-2}{5}>\frac{-3}{7}\)

THANK YOU

a)\(\frac{1}{n}-\frac{1}{n+1}=\frac{n+1-n}{n\left(n+1\right)}=\frac{1}{n\left(n+1\right)}\)

suy ra (đề bài)

b)\(A=\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{9.10}=1-\frac{1}{2}+\frac{1}{2}-...-\frac{1}{10}=1-\frac{1}{10}=\frac{9}{10}\)

bn ơi chờ tí mình ăn cơm đã nhé

\(\frac{1}{3}+\frac{13}{15}+\frac{33}{35}+...+\frac{9997}{9999}=1-\frac{2}{3}+1-\frac{2}{15}+1-\frac{2}{35}+...+1-\frac{2}{9999}\)

\(=\left(1+1+1+...+1\right)-\left(\frac{2}{3}+\frac{2}{15}+\frac{2}{35}+...+\frac{2}{9999}\right)\)

\(=50-\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{99.101}\right)\)

\(=50-\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{99}-\frac{1}{101}\right)\)

\(=50-\left(1-\frac{1}{101}\right)=50-\frac{100}{101}=\frac{4950}{101}\)

thank you bạn nhé mình sẽ k cho bạn