\(1\cdot2\cdot3\cdot4\cdot6⋮̸10\)

\(1\cdot2\cdot3\cdot4\cdot5\cdot6\cdot7⋮10\)

Do đó: \(1\cdot2\cdot3\cdot4\cdot6+1\cdot2\cdot3\cdot4\cdot5\cdot6\cdot7⋮̸10\)

B = 1.2.3.4.6

B là tích của các số chwaxn mà trong đó không có nào có tận cùng bằng 0 nên B không chia hết cho 10

A = 1.2.3.4.5.6.7

A = (2.5). 1.3.4.6.7 = 10.1.3.4.6.7 ⋮ 10

Vậy B + A không chia hết cho 10 

\(697:15\cdot x+\dfrac{364}{x}=17\)

=>\(\dfrac{697x}{15}+\dfrac{364}{x}=17\)

=>\(\dfrac{697x^2+5460}{15x}=17\)

=>\(697x^2+5460-255x=0\)

=>\(x\in\varnothing\)

bạn nguyễn lê phước thịnh cho mik hỏi ở phần 697X2 +5460/15x thì 5460 ở đâu vậy ạ

have already read nhé

Ta có: \(\left(1+\dfrac{1}{3}\right)\times\left(1+\dfrac{1}{8}\right)\times...\times\left(1+\dfrac{1}{9999}\right)\)

\(=\left(1+\dfrac{1}{2^2-1}\right)\times\left(1+\dfrac{1}{3^2-1}\right)\times....\times\left(1+\dfrac{1}{100^2-1}\right)\)

\(=\dfrac{2^2}{2^2-1}\times\dfrac{3^2}{3^2-1}\times...\times\dfrac{100^2}{100^2-1}\)

\(=\dfrac{2\times3\times...\times100}{1\times2\times...\times99}\times\dfrac{2\times3\times...\times100}{3\times4\times...\times101}=\dfrac{100}{1}\times\dfrac{2}{101}=\dfrac{200}{101}\)

1 Does Simon help

helps

2 are you doing

am writing - write

3 is snowing - is coming

1 Does Simon help - is helping

2 are you doing - am writing - write

3 is snowing - is coming 

\(\dfrac{255}{315}=\dfrac{255\div15}{315\div15}=\dfrac{17}{21}\)

D.

3.[(2\(x\) + 10): \(x\)] = 12 (\(x\ne\) 0)

   (2\(x\) + 10):\(x\) = 12 : 3

   (2\(x\) + 10) : \(x\)  = 4

   2\(x\) + 10 = 4 x \(x\) 

   4\(x\) - 2\(x\) = 10

    2\(x\) = 10

     \(x=10:2\)

    \(x=5\)

Vậy \(x=5\) 

\(3\left[\dfrac{2x+10}{x}\right]=12\)

=>\(\dfrac{3\left(x+5\right)}{x}=6\)

=>3(x+5)=6x

=>2x=x+5

=>2x-x=5

=>x=5

\(x:5,1+x:0,17-x=518\)

=>\(x\cdot\left(\dfrac{1}{5,1}+\dfrac{1}{0,17}-1\right)=518\)

=>\(x\cdot\dfrac{259}{51}=518=259\cdot2\)

=>\(x=259\cdot2:\dfrac{259}{51}=2\cdot51=102\)

AM=1/4MB

=>MB=4AM

AM+MB=AB

Do đó: 4AM+MA=8

=>5MA=8

=>\(MA=\dfrac{8}{5}=1,6\left(cm\right)\)

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