Question

tìm n thuộc N biết :

( 2n - 1 )^2 = 121

Answer 1

(2n-1)² = 121

=> 2n-1 = 11

2n = 11+1

2n = 12

n = 12:2

n = 6

Answer 2

\(\left(2n-1\right)^2=121\)

\(\Leftrightarrow\left(2n-1\right)^2=\orbr{\begin{cases}11^2\\\left(-11\right)^2\end{cases}}\)

Do \(n\in N\)\(\Rightarrow\)\(\left(2n-1\right)^2=11^2\)

\(\Leftrightarrow2n-1=11\)

\(\Leftrightarrow2n=12\)

\(\Leftrightarrow n=6\)

Answer 3

(2n-1)^2=121

=>(2n-1)^2=11^2

=>2n-1=11

2n=12

n=6

Vậy n=6