Question

[thuỳ handan]

a, (2n-1)³ - 125² = 0

b, n²⁰ = 1ⁿ

c, 5ⁿ . 5ⁿ⁺¹ . 5ⁿ⁺² < hoac = 100..00 : 2¹⁸

(số 100...0 có 18 c/s 0 nhé )

Answer 1

[Lê Bùi]

a)\(\left(2n-1\right)^3=5^3\)

\(\Leftrightarrow2n-1=5\Rightarrow n=3\)

b)\(n^{20}=1\)(vì \(1^n=1\))

\(\Rightarrow n=1\)

c)\(5^{3n+3}\le\dfrac{10^{18}}{2^{18}}\)

\(\Leftrightarrow5^{3n+3}\le5^{18}\)

\(\Leftrightarrow3n+3\le18\)

\(\Rightarrow n\le5\)