a)\(\frac{x-1}{x+2}=\frac{4}{5}\Leftrightarrow5\left(x-1\right)=4\left(x+2\right)\Leftrightarrow5x-5=4x+8\Leftrightarrow x=13\)

b)\(\frac{1}{12}:\frac{4}{21}=3\frac{1}{2}:\left(3x-2\right)\Leftrightarrow\frac{21}{48}=\frac{7}{2}:\left(3x-2\right)\Leftrightarrow\frac{7}{2}:\frac{21}{48}=3x-2\Leftrightarrow x=\frac{10}{3}\)

c)\(x^3=27.-8=>x^3=-216=>x=-6\)

d)\(=>\left(x+7\right)^2=100\Leftrightarrow\orbr{\begin{cases}x+7=10\\x+7=-10\end{cases}=>\orbr{\begin{cases}x=3\\x=-17\end{cases}}}\)

e\(-x^4=-16=>\orbr{\begin{cases}x=2\\x=-2\end{cases}}\)

f)\(x^4=8x=>x^4-8x=0=.x\left(x^3-8\right)=>\orbr{\begin{cases}x=0\left(loại\right)\\x=2\end{cases}}\)

cứu mik vs

sorry chị em mới lớp 6 nên ko biết làm mong chị thông cảm ạ

có cái con

1/2x+5/2=7/2x-3/4

7/2x-1/2x=5/2+3/4

3x=13/4

x=13/12

\(\frac{1}{2}x+\frac{5}{2}=\frac{7}{2}x-\frac{3}{4}\)

\(\Leftrightarrow\frac{1}{2}x-\frac{7}{2}x=-\frac{3}{4}-\frac{5}{2}\)

\(\Leftrightarrow-3x=-\frac{13}{4}\)

\(\Leftrightarrow x=\frac{13}{12}\)

Vậy \(x=\frac{13}{12}\).

Ta có: 1/2x - 2/5 = 1/2x - 1/3

           1/2x = -2/5 + 1/3

           1/2x = -1/15

               x= -2/15

Khi x = 9 

=> x + 1 = 10

Khi đó P(9) = x⁵⁰ - (x + 1)x⁴⁹ + (x + 1)x⁴⁸ - (x + 1)x⁴⁷ + ... + (x + 1)x - 1

= x⁵⁰ - x⁵⁰ - x⁴⁹ + x⁴⁹ + x⁴⁸ - x⁴⁸ - x⁴⁷ + ... + x² + x - 1

= x - 1 

= 9 - 1 = 8 

=8

tốt

hok

nha