\(\Rightarrow5x=30\)

\(\Rightarrow x=6\)

\(5x-13=17\)
\(5x=30\)
\(x=6\)

5x-13=17

5x=13+17

5x= 30

x=30:5

x=6. 

Vậy x=6

\(5x+5x^2=43x^3\\ \Rightarrow43x^3-5x^2-5x=0\\ \Rightarrow x\left(43x^2-5x-5\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=0\\43x^2-5x-5=0\left(1\right)\end{matrix}\right.\\ \Delta\left(1\right)=25+4.5.43=885\\ \Rightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{5+\sqrt{885}}{86}\\x=\dfrac{5-\sqrt{885}}{86}\end{matrix}\right.\)

\(\Leftrightarrow5x=-630+120=-510\)

hay x=-102

X x 4 = 160                                                                        X : 5 = 151

X       = 160 : 4                                                                   X      = 151 x 5

X       = 40                                                                           X      = 755

Đáp án cần chọn là: A

−8.x=160

x=160:(−8)

x=−20

b) 16020 : x = 45

x = 16020 : 45

x = 356

\(\left(x+16\right)\left(x+56\right)=160\)

\(\Leftrightarrow x^2+56x+16x+896=160\)

\(\Leftrightarrow x^2+72x+896=160\)

\(\Leftrightarrow x^2+72x+1296-400=160\)

\(\Leftrightarrow\left(x+36\right)^2=560\)

\(\Leftrightarrow\orbr{\begin{cases}x+36=\sqrt{560}\\x+36=-\sqrt{560}\end{cases}}\Rightarrow\orbr{\begin{cases}x=4\sqrt{35}-36\\x=-4\sqrt{35}-36\end{cases}}\)

`( 42 - x ) : 9 + 1 = 4`

`( 42 - x ) : 9 =4-1`

`( 42 - x ) : 9 =3`

`42-x=3xx9`

`42-x=27`

`x=42-27`

`x=15`

Vậy `=15`

`55 - 5 xx ( x + 1 ) = 20`

`5 xx ( x + 1 ) =55-20`

`5 xx ( x + 1 ) =35`

`x+1=35:5`

`x+1=7`

`x=7-1`

`x=6`

Vậy `x=6`

`164 - 64 : ( 12 + x ) = 160`

` 64 : ( 12 + x ) =164-160`

` 64 : ( 12 + x ) =4`

`12+x=64:4`

`12+x=16`

`x=16-12`

`x=2`

Vậy `x=2`

`@` `\text {Ans}`

`\downarrow`

`(42 - x) \div 9 + 1 = 4`

` (42 - x) \div 9 = 4 - 1`

` (42 - x) \div 9 = 3`

` 42 - x = 3 \times 9`

` 42 - x = 27`

` x = 42 - 27`

` x = 15`

______

`55 - 5 \times ( x + 1 ) = 20`

`5 \times (x+1) = 55 - 20`

`5 \times (x+1) = 35`

`x + 1 = 35 \div 5`

`x + 1 = 7`

`x = 7 - 1`

`x = 6`

______

`164 - 64 \div ( 12 + x ) = 160`

`64 \div (12 + x) = 164 - 160`

`64 \div (12 + x) = 4`

`12 + x = 64 \div 4`

`12 + x = 16`

`x = 16 - 12`

`x = 4`

`@` `\text {Kaizuu lv uuu}`

\(\left(42-x\right):9+1=4\)

\(\left(42-x\right):9=4-1\)

\(\left(42-x\right):9=3\)

\(42-x=3\times9\)

\(42-x=27\)

\(x=42-27\)

\(x=15\)

\(55-5\times\left(x+1\right)=20\)

\(5\times\left(x+1\right)=55-20\)

\(5\times\left(x+1\right)=35\)

\(x+1=35:5\)

\(x+1=7\)

\(x=7-1\)

\(x=6\)

\(164-64:\left(12+x\right)=160\)

\(64:\left(12+x\right)=164-160\)

\(64:\left(12+x\right)=4\)

\(12+x=64:4\)

\(12+x=16\)

\(x=16-12\)

\(x=4\)

Theo đề bài ta có : x là ƯCLN (150,160)

150=2x3x5²

160=2⁵ x5

\(ƯCLN\left(150,160\right)=2\times5=10\)

=> x=10

150 chia hết x; 160 chia hết cho x => \(x\in UCLN\left(150;160\right)\)

ƯC(150;160) = {1;-1;2;-2;....}

Số x là....... tự tìm nha

Đáp án cần chọn là: B