4x+x-15=55

=>5x=55+15=70

=>\(x=\dfrac{70}{5}=14\)

= 4.x+x=55-15

=4.x+x=40

=x(4+1)=40

=x.5=40

=x=40:5

=x=8

Chúc bạn học tốt ^^

\(5n+12⋮n-5\)

=>\(5n-25+37⋮n-5\)

=>\(37⋮n-5\)

=>\(n-5\in\left\{1;-1;37;-37\right\}\)

=>\(n\in\left\{6;4;42;-32\right\}\)

mà n>=0

nên \(n\in\left\{6;4;42\right\}\)

`5n + 12 ⋮ n - 5`

`=> 5n - 25 + 37  ⋮ n - 5`

`=> 5(n - 5) + 37  ⋮ n - 5`

Do `n+5  ⋮ n - 5 `

`=> 5(n+5)  ⋮ n - 5`

`=> 37  ⋮ n - 5`

`=> n - 5` thuộc `Ư(37) =` {`-37;-1;1;37`}

`=> n` thuộc {`-32;4;6;42`}

Mà `n` thuộc `N`

`=> n` thuộc {`4;6;42`}

Vậy ...

\(\overline{abc0cd}\\ =a\cdot100000+b\cdot10000+c\cdot1000+0\cdot100+c\cdot10+d\\ =a\cdot10^5+b\cdot10^4+c\cdot10^3+0\cdot10^2+c\cdot10+d\)

\(\overline{abc0cd}=a\cdot10^5+b\cdot10^4+c\cdot10^3+0\cdot10^2+c\cdot10+d\)

\(=a\cdot10^5+b\cdot10^4+c\left(10^3+10\right)+d\)

a: \(11^2=11\cdot11=121;111^2=12321\)

b: Dự đoán: \(1111^2=1234321\)

Tính: \(1111^2=1111\cdot1111=1234321\)

trình bày và giải thích giups em đk ạ

`5^2 . 11 + 5^2 . 19`

`= 5^2 . (11+19)`

`= 25 . 30`

`= 750`

2020

2020

\(m.\left(\dfrac{14}{3}+\dfrac{14}{15}+...+\dfrac{14}{195}\right)=1\)

=> \(m.7.\left(\dfrac{2}{1.3}+\dfrac{2}{3.5}+...+\dfrac{2}{13.15}\right)=1\)

=> \(7m.\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+...+\dfrac{1}{13}-\dfrac{1}{15}\right)=1\)

=> \(7m.\left(1-\dfrac{1}{15}\right)=1\)

=> \(\dfrac{7m.14}{15}=1\)

=> \(m=\dfrac{15}{98}\)

`3^3 - 2^2 . 5 + 125 : 5`

`= 27 - 4 . 5 +` \(\dfrac{125}{52}\)

`= 27 - 20 +` \(\dfrac{125}{52}\)

`= 7 +` \(\dfrac{125}{52}\)

`=` \(\dfrac{7.52+125}{52}\)

`=` \(\dfrac{489}{52}\)

\(3^3-2^2\cdot5+125:52\)

= \(27-4\cdot5+\dfrac{125}{52}\)

= \(27-20+\dfrac{125}{52}\)

= \(7+\dfrac{125}{52}\)

= \(\dfrac{52\cdot7+125}{52}\)

= \(\dfrac{489}{52}\)

`(x + 7) - 25 = 13`

`=> x +7 = 13 + 25`

`=> x+ 7 = 38`

`=> x = 38 - 7`

`=> x = 31`

Vậy `x=31`

\(\left(x+7\right)-25=13\)

\(x+7=13+25\)

\(x+7=38\)

\(x=38-7\)

\(x=31\)

vậy x = 31