Ta có : 4³⁰ = (2²)³⁰ = 2^2.30 = 2⁶⁰

Lại có : 8²⁰ = (2³)²⁰ = 2^3.20 = 2⁶⁰

Vì 2⁶⁰ = 2⁶⁰

=> 4³⁰ = 8²⁰

4³⁰ = ( 4³ )¹⁰ = 64¹⁰

8²⁰ = ( 8² )¹⁰ = 64¹⁰

=> 4³⁰ = 8²⁰

theo tính chất dãy tỉ số bằng nhau

có \(\frac{x}{5}=\frac{y}{7}=\frac{z}{2}=\frac{y-x}{7-5}=\frac{48}{2}=24\)

do đó 

\(\Rightarrow\frac{x}{5}=24\Leftrightarrow x=5.24=120\)

\(\Rightarrow\frac{y}{7}=24\Leftrightarrow y=7.24=168\)

\(\Rightarrow\frac{z}{2}=24\Leftrightarrow z=2.24=48\)

vậy ...

Ta có : \(\frac{x}{5}=\frac{y}{7}=\frac{z}{2}=\frac{y-x}{7-5}=\frac{48}{2}=24\)(áp dụng tính chất dãy tỉ số bằng nhau)

=> \(\hept{\begin{cases}\frac{x}{5}=24\\\frac{y}{7}=24\\\frac{z}{2}=24\end{cases}}\Rightarrow\hept{\begin{cases}x=120\\y=168\\z=48\end{cases}}\)

Trả lời:

\(B=\left(x-3\right).\left(x+3\right).\left(x^2+9\right)-\left(x^2+2\right).\left(x^2-2\right)\)

\(B=\left(x^2-9\right).\left(x^2+9\right)-\left(x^4-4\right)\)

\(B=\left(x^4-81\right)-\left(x^4-4\right)\)

\(B=x^4-81-x^4+4\)

\(B=-77\)

bài nayfd dễ

a) Đa thức bậc nhất chỉ có 1 và chỉ 1 nghiệm duy nhất

Cảm ơn a, vậy a chứng minh điều đó e xem vs ạ

|7/5x + 3/4| - |4/3 - 1/4| = 0

=> |7/5x + 3/4| - 13/12 = 0

=> |7/5x + 3/4| = 13/12

=> \(\orbr{\begin{cases}\frac{7}{5}x+\frac{3}{4}=\frac{13}{12}\\\frac{7}{5}x+\frac{3}{4}=-\frac{13}{12}\end{cases}}\Rightarrow\orbr{\begin{cases}\frac{7}{5}x=\frac{1}{3}\\\frac{7}{5}x=-\frac{11}{6}\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{5}{21}\\x=-\frac{55}{42}\end{cases}}\)

\(\left|\frac{7}{5}x+\frac{3}{4}\right|-\left|\frac{4}{3}-\frac{1}{4}\right|=0\)

\(\Rightarrow\left|\frac{7}{5}x+\frac{3}{4}\right|-\frac{13}{12}=0\)

\(\Rightarrow\left|\frac{7}{5}x+\frac{3}{4}\right|=\frac{13}{12}\)

\(\Rightarrow\orbr{\begin{cases}\frac{7}{5}x+\frac{3}{4}=\frac{13}{12}\\\frac{7}{5}x+\frac{3}{4}=-\frac{13}{12}\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}\frac{7}{5}x=\frac{1}{3}\\\frac{7}{5}x=-\frac{11}{6}\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=\frac{5}{21}\\x=-\frac{55}{42}\end{cases}}\)

5 + 1/2 - 2/3

= 10/2 + 1/2 -2/3

= 11/2- 2/3

= 33/6- 4/6

= 29/6

(6-5/2):3/2

= (12/2 - 5/2):3/2

= 7/2 : 3/2

= 7/2. 2/3

=7/3

5 + 1/2 - 2/3

(6 - 5/2): 3/2

1)   5 + 1/2 - 2/3
 = 10/2 + 1/2 -2/3
 = 11/2- 2/3
 = 33/6- 4/6
= 29/6
2)   (6-5/2):3/2
 = (12/2 - 5/2):3/2
 = 7/2 : 3/2
 = 7/2x 2/3
 =7/3

a) \(\frac{0,5}{0,2}=\frac{1,25}{0,1x}\Leftrightarrow0,1x.0,5=0,2.1,25\)

\(\Leftrightarrow0,1x.0,5=0,25\Leftrightarrow0,1x=0,5\Leftrightarrow x=5\)

b) \(x-\frac{3}{2}=2x-\frac{4}{3}\Leftrightarrow x-2x=\frac{-4}{3}+\frac{3}{2}\)
\(\Leftrightarrow x-2x=\frac{1}{6}\Leftrightarrow-x=\frac{1}{6}\Leftrightarrow x=\frac{-1}{6}\)

c) \(x+\frac{13}{14}=\frac{4}{7}\Rightarrow x=\frac{4}{7}-\frac{13}{14}\Rightarrow x=\frac{-5}{14}\)

d)\(-3\left(x-2\right)=2x+1\)

\(\Leftrightarrow-3x+6=2x+1\Leftrightarrow-3x-2x=1-6\)

\(\Leftrightarrow-5x=-5\Leftrightarrow x=1\)

e) \(\left(x-1\right)^2-4=0\Leftrightarrow\left(x-1\right)^2=4\)

\(\Leftrightarrow\orbr{\begin{cases}x-1=2\\x-1=\left(-2\right)\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=3\\x=-1\end{cases}}\)

cậu có thể tham khảo bài trên ạ, nếu thấy đúng thì cho mk 1 t.i.c.k ạ, thank nhiều

\(d,-3\left(x-2\right)=2x+1\)

\(< =>-3x+6=2x+1\)

\(< =>-3x-2x+6-1=0\)

\(< =>5-5x=0\)

\(< =>5\left(1-x\right)=0< =>x=1\)

\(e,\left(x-1\right)^2-4=0\)

\(< =>\left(x-1+2\right)\left(x-1-2\right)=\left(x+1\right)\left(x-3\right)=0\)

\(< =>\orbr{\begin{cases}x+1=0\\x-3=0\end{cases}< =>\orbr{\begin{cases}x=-1\\x=3\end{cases}}}\)

Trả lời :

\(A=\frac{3}{4}\times\frac{5}{9}+\frac{6}{7}\times\frac{3}{4}-\frac{7}{5}\times\frac{3}{4}\)

\(\Rightarrow A=\frac{3}{4}\times\left(\frac{5}{9}+\frac{6}{7}-\frac{7}{5}\right)\)

\(\Rightarrow A=\frac{3}{4}\times\frac{4}{315}\)

\(\Rightarrow A=\frac{3}{315}=\frac{1}{105}\)

Trả lời:

\(A=\frac{3}{4}\times\frac{5}{9}+\frac{6}{7}\div\frac{4}{3}-1\frac{2}{5}\div1\frac{1}{3}\)

\(A=\frac{3}{4}\times\frac{5}{9}+\frac{6}{7}\times\frac{3}{4}-\frac{7}{5}\div\frac{4}{3}\)

\(A=\frac{3}{4}\times\frac{5}{9}+\frac{6}{7}\times\frac{3}{4}-\frac{7}{5}\times\frac{3}{4}\)

\(A=\frac{3}{4}\times\left(\frac{5}{9}+\frac{6}{7}-\frac{7}{5}\right)\)

\(A=\frac{3}{4}\times\frac{4}{315}\)

\(A=\frac{1}{105}\)

Học tốt 

\(\frac{2a-3b}{a+b}=\frac{1}{2}\)
\(\Rightarrow2.\left(2a-3b\right)=a+b\)
\(\Rightarrow4a-6b=a+b\)
\(\Rightarrow4a-a=b+6b\)
\(\Rightarrow3a=7b\)
\(\Rightarrow\frac{a}{b}=\frac{7}{3}\)

\(\frac{2a-3b}{a+b}=\frac{1}{2}\)

\(\Leftrightarrow2.\left(2a+3b\right)=1.\left(a+b\right)\)

\(\Leftrightarrow4a+6b=a+b\)

\(\Leftrightarrow4a+6b-a-b=0\)

\(\Leftrightarrow3a+5b=0\)

\(\Leftrightarrow3a=5b\)

\(\Leftrightarrow a=\frac{5}{3}b\)

\(\Leftrightarrow\frac{a}{b}=\frac{5}{3}\)

Cái này k thể tìm ra kết quả của a và b được nha \(\frac{a}{b}=\frac{5}{3}\)chỉ là a:b=5:3 thôi

Chúc bạn học tốt

\(\frac{2a+3b}{a+b}=\frac{1}{2}\)\(\Leftrightarrow2\left(2a+3b\right)=a+b\)

\(\Leftrightarrow4a+6b=a+b\)

\(\Leftrightarrow4a-a=b-6b\)

\(\Leftrightarrow3a=-5b\)\(\Leftrightarrow\frac{a}{b}=\frac{-5}{3}\)

Vậy \(\frac{a}{b}=\frac{-5}{3}\)

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