a) x6 + x4 = 0

=> x⁴ . ( x² + 1 ) = 0

\(\Rightarrow\hept{\begin{cases}x^4=0\\x^2+1=0\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}x=0\\x^2=-1\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}x=0\\x∈Ø \left(\text{ do }x^2≥0∀x\right)\end{cases}}\)

b) \(\left|-x+\frac{5}{3}\right|-2=3\frac{1}{3}\)

\(\Rightarrow\left|\frac{5}{3}-x\right|=3\frac{1}{3}+2=5\frac{1}{3}\)

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

\(\Rightarrow\orbr{\begin{cases}x=\frac{5}{3}-5\frac{1}{3}\\x=\frac{5}{3}-\left(-5\frac{1}{3}\right)\end{cases}}\)

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

\(a)2\left(x+3\right)-x^2-3x=0\)

\(\Leftrightarrow2x+6-x^2-3x=0\)

\(\Leftrightarrow-x^2+2x-3x+6=0\)

\(\Leftrightarrow-x^2-x+6=0\)

\(\Leftrightarrow x^2+x-6=0\)

\(\Leftrightarrow x^2+3x-2x-6=0\)

\(\Leftrightarrow x\left(x+3\right)-2\left(x+3\right)=0\)

\(\Leftrightarrow\left(x+3\right)\left(x-2\right)=0\)

\(\Leftrightarrow x+3=0\) hoặc  \(x-2=0\)

\(\Leftrightarrow x=-3\) hoặc  \(x=2\)

\(b)4x^2-25-\left(2x-5\right)\left(2x+7\right)=0\)

\(=\left(2x-5\right)\left(2x+5\right)-\left(2x-5\right)\left(2x+7\right)=0\)

\(=\left(2x-5\right)\left(2x+5-2x-7\right)=0\)

\(=-2\left(2x-5\right)=0\)

\(=2x-5=0\Leftrightarrow x=\frac{5}{2}\)

Cảm ơn bạn rất nhiều

\(c,\frac{8^{13}.27^{18}}{6^{17}.18^{19}}=\frac{\left(2^3\right)^{13}.\left(3^3\right)^{18}}{\left(2.3\right)^{17}.\left(2.3^3\right)^{19}}\)

\(=\frac{2^{39}.3^{54}}{2^{17}.3^{17}.2^{19}.3^{57}}=\frac{2^{39}.3^{54}}{2^{36}.3^{74}}\)

\(=\frac{2^3}{3^{20}}\)

\(8^9\) và \(9^8\)

\(8^9=\left(8^3\right)^3=512^3\)

\(9^8=\left(9^2\right)^4=81^4\)

\(81^4=81^3.81\)

Mà \(81^3< 512^3\)

\(\Rightarrow512^3>81^3.81\)

Vậy \(8^9>9^8\)

Lời giải:

$8^9={\left(8^3\right)}^3={512}^3$

$9^8={\left(9^2\right)}^4={81}^4$

${81}^4={81}^3\cdot 81$

Mà ${81}^3<{512}^3$

$\Rightarrow {512}^3>{81}^3\cdot 81$

Vậy $8^9>9^8$

https://www.youtube.com/watch?v=Sfnz7tPvXRE

Link vào đây để nghe nhạc và xem video nhé

1 người đánh mất mấy giờ là:

8x5=40(giờ)

8 người dánh xong hết số giờ là:

40:8=5(giờ

HT