Bài 4: Cộng hai số nguyên cùng dấu

(-68) + (-72) + 2017 +(-28) +168= -(68+72+28)+2017+168=(-168)+2017+168=2017

-249

\(-7+\left(-5\right)=-\left(7+5\right)=-12\)

-7 + -5 = - ( 7 + 5 ) = - 12

Vậy -7 + -5 = -12

-7+-5=-12

=35+15=50

kết quả là:

= 35+15= 50

nhớ tick cho mình nha

50

-12+(-123)-(-1234)-(-12345)

=-12+(-123)+1234+12345

=-135+1234+12345

=(-135+12345)+1234

=12210+1234

=13444

-12 + (-123)-(-1234)-(-12345)

= -135 +1234 +12345

= -135 + 13579

= 13444

B1:

\(n^2+2n-7⋮n+2\)

\(\Leftrightarrow n\left(n+2\right)-7⋮n+2\)

Vì \(n\left(n+2\right)⋮n+2\Rightarrow-7⋮n+2\)

\(\Rightarrow n+2\inƯ\left(-7\right)=\left\{-1;1;-7;7\right\}\)

Ta có bảng sau:

Vậy để \(n^2+2n-7⋮n+2\) thì \(n\in\left\{-9;-3;-1;5\right\}\)

a,|x|+3=5

\(\Leftrightarrow\left|x\right|=5-3=2\)

\(\Rightarrow x=\left\{{}\begin{matrix}2\\-2\end{matrix}\right.\)

b,|x+3|=5

\(\Rightarrow\left\{{}\begin{matrix}x+3=5\\x+3=-5\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}2\\-8\end{matrix}\right.\)

c,|x-7|+13=25

<=>|x-7|=25-13=12

\(\Rightarrow\left\{{}\begin{matrix}x-7=12\\x-7=-12\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=19\\x=-5\end{matrix}\right.\)

d,\(26-\left|x+9\right|=-13\)

\(\Leftrightarrow\left|x+9\right|=26-\left(-13\right)=39\)

\(\Rightarrow\left\{{}\begin{matrix}x+9=39\\x+9=-39\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=30\\x=-48\end{matrix}\right.\)

e,8-|x|=15

<=>|x|=8-15=-7

\(\Rightarrow\left\{{}\begin{matrix}x=-7\\x=7\end{matrix}\right.\)

f,6-|-3+x|=-15

\(\Leftrightarrow\left|-3+x\right|=6-\left(-15\right)=21\)

\(\Rightarrow\left\{{}\begin{matrix}-3+x=21\\-3+x=-21\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=24\\x=-18\end{matrix}\right.\)

a, |x| + 3 = 5

|x| = 5 - 3

|x| = 2

|x| = 2 hoặc |x| = -2

Vậy |x| thuộc {2; -2}

b,|x + 3| = 5

|x + 3| = 5 hoặc |x + 3| = -5

x = 5 - 3 x = (-5) - 3

x = 2 x = -8

Vậy x thuộc {2; -8}

c,|x - 7| + 13 = 25

|x - 7| = 25 - 13

|x - 7| = 12

|x - 7| = 12 hoặc |x - 7| = -12

x = 12 + 7 x = (-12) + 7

x = 19 x = -5

Vậy x thuộc {19 ; -5}

a,|x|+3=5

b,|x+3|=5

c,|x-7|+13=25

<=>|x-7|=25-13=12

d,

e,8-|x|=15

<=>|x|=8-15=-7

f,6-|-3+x|=-15

1 + |11| + (-12)

= 1 + 11 + (-12)

= 12 + (-12)

= 0

=1+11+(-12)

=12+(-12)

=0

1+|11|+(-12)

=1+11-12

=12-12

=0

\(\left|x\right|+3=7\)

\(\left|x\right|=4\)

\(\Leftrightarrow\left[{}\begin{matrix}x=4\\x=-4\end{matrix}\right.\)

Vậy...

|x| + 3 = 7

|x| = 7 - 3

|x| = 4

\(\Rightarrow\left\{{}\begin{matrix}x=4\\x=-4\end{matrix}\right.\)

Vậy x = 4 hoặc - 4

ặc

ậy ặc x=−4