Dễ mà bạn!

cậu tự làm đi

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a) 45^x : 5^x = 81

=> ( 45 : 5 )^x = 81

=> 9^x = 9²

=> x = 2

a) 45^x : 5^x = 81 <=> (45 : 5)^x = 81 <=> 9^x = 9² => x = 2

b) 7^{(x + 1)(2x - 3)} = 1

<=> 7^{(x + 1)(2x - 3)} = 7⁰

=> (x + 1)(2x - 3) = 0

<=> \(\orbr{\begin{cases}x+1=0\\2x-3=0\end{cases}}\)<=> \(\orbr{\begin{cases}x=-1\\x=\frac{3}{2}\end{cases}}\)

c) 4^x+1 - 2^2x = 192

<=> 4^x.4 - 4^x = 192

<=> 4^x . 3 = 192

<=> 4^x = 64

<=> 4^x = 4³ => x = 3

d) x³ - 4x = 0

<=> x(x² - 4)) = 0

<=> \(\orbr{\begin{cases}x=0\\x^2-4=0\end{cases}}\)

<=> \(\orbr{\begin{cases}x=0\\x=\pm2\end{cases}}\)

\(\frac{x}{2}=\frac{y}{3}\Rightarrow\frac{4y}{12}=\frac{3x}{6}\)

THeo tcdtsbn ta có:

\(\frac{4y}{12}=\frac{3x}{6}=\frac{4y-3x}{12-6}=\frac{5}{6}\)

\(\Rightarrow\frac{x}{2}=\frac{y}{3}=\frac{5}{6}\)

\(\Rightarrow x=\frac{5}{3};y=\frac{5}{2}\)

6 miền

k mình

nha

đúng

\(C=-\left(\frac{3}{7}+\frac{3}{8}\right)-\left(-\frac{3}{8}+\frac{4}{7}\right).\)

\(C=-\frac{45}{56}-\frac{11}{56}\)

\(C=-1\)

\(C=-\left(\frac{3}{7}+\frac{3}{8}\right)-\left(-\frac{3}{8}+\frac{4}{7}\right)\)

\(C=-\frac{3}{7}-\frac{3}{8}+\frac{3}{8}-\frac{4}{7}\)

\(C=-\frac{3}{7}-\frac{4}{7}\)

\(C=-\frac{7}{7}=-1\)

F = x⁴ - 2x² + 3 = x⁴ - 2x² + 1 + 2 = (x² - 1)² + 2 \(\ge2\)

=> Min F = 2

Dấu "=" xảy ra <=> x² - 1 = 0

<=> x = \(\pm1\)

Vậy Min F = 2 <=> x = \(\pm1\)

Ta có G = (x² + 2)² - 3 

= x⁴ + 4x² + 1 = x²(x² + 4) + 1 \(\ge1\)

=> Min G = 1

Dấu "=" xảy ra <=> x²(x² + 4) = 0 

<=> x = 0

Vậy Min G = 1 <=> x = 0

dạng 3 ko cần làm