\(\Rightarrow5x=30\)

\(\Rightarrow x=6\)

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

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

lớp 7 đã học Delta đâu a

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

hay x=-102

Bài 10:

a: x-5=-1

=>x=-1+5

=>x=4

b: x+30=-4

=>x=-4-30

=>x=-34

c: x-(-24)=3

=>x+24=3

=>x=3-24

=>x=-21

d: 22-(-x)=12

=>22+x=12

=>x=12-22

=>x=-10

e: (x+5)+(x-9)=x+2

=>x+5+x-9=x+2

=>2x-4=x+2

=>2x-x=4+2

=>x=6

f: (27-x)+(15+x)=x-24

=>x-24=27-x+15+x=42

=>x=42+24

=>x=66

Bài 9:

a: 15-(4-x)=6

=>4-x=15-6=9

=>x=4-9=-5

b: -30+(25-x)=-1

=>-30+25-x=-1

=>-5-x=-1

=>x+5=1

=>x=1-5

=>x=-4

c: x-(12-25)=-8

=>x-(-13)=-8

=>x+13=-8

=>x=-8-13

=>x=-21

d: (x-29)-(17-38)=-9

=>x-29-(-21)=-9

=>x-29+21=-9

=>x-8=-9

=>x=-9+8

=>x=-1

Bài 8:

a: (17-229)+(17-25+229)

=17-229+17-25+229

=34-25

=9

b: (125-679+145)-(125-679)

=125-679+145-125+679

=145

\(x^3\) + 125 + (\(x\) + 5)(\(x\) - 25) = 0

(\(x^3\) + 5³) + (\(x\) + 5)(\(x\) - 25) = 0

(\(x\) + 5)(\(x^2\) - 5\(x\) + 25) + (\(x\) + 5)(\(x\) - 25) =0

(\(x\) + 5)(\(x^2\) - 5\(x\) + 25 + \(x\) - 25) = 0

(\(x\) + 5)(\(x^2\) - 4\(x\)) = 0

\(x\)(\(x\) + 5)(\(x\) - 4) = 0

\(\left[{}\begin{matrix}x=0\\x+5=0\\x-4=0\end{matrix}\right.\)

\(\left[{}\begin{matrix}x=0\\x=-5\\x=4\end{matrix}\right.\)

`x^3 + 125 + (x + 5)(x - 25) = 0`

`<=>(x + 5)(x^2 + 5x + 25) + (x + 5)(x - 25) = 0`

`<=>(x + 5)(x^2 + 6x) = 0`

`<=>x(x + 5)(x + 6) = 0`

`<=>x = 0` hoặc `x = -5` hoặc `x=-6`

Chọn đáp án B.

\(\left(x+5\right)+\left(x+10\right)+...+\left(x+25\right)-125=150\)
\(\Leftrightarrow x+5+x+10+...+x+25-125=150\)
\(\Leftrightarrow5x-50=150\)
\(\Leftrightarrow5x=100\)
\(\Leftrightarrow x=\dfrac{100}{5}=20\)
Vậy \(x=20\)

x = 20

\(x\times125-x\times25=37800\\ \Rightarrow x\times\left(125-25\right)=37800\\ \Rightarrow x\times100=37800\\ x=378\)

Cảm ơn bạn nhiều nha :3

x + x + 25 = 125

ta có : 2x + 25 = 125

                  2x = 125 - 25

                  2x = 100

                    x = 50

k mik nha

x + x + 25 = 125

 =>2x+25=125

=>2x=125-25

=>2x=100

=>x=100:2

=>x=50

k nha