Question

tìm số nguyên x biết : 

x^2-1=80

Answer 1

x²-1=80

x²    = 80+1

x²    =81

Vì 9²=81

nên x²=9²

Vậy x=9

Answer 2

\(x^2-1=80\)

\(x^2=80+1\)

\(x^2=81\)

\(x^2=9^2\)

\(\Rightarrow x=9\)

Answer 3

x^2-1=80

x^2=80+1

x^2=81

x^2=9^2

=> x=9

Vậy x=9

Answer 4

\(x^2-1=80\)

\(x^2\)     \(=80+1\)

\(x^2\)     \(=81\)

\(x^2\)     \(=9^2\)

\(\Rightarrow\orbr{\begin{cases}x=9\\x=-9\end{cases}}\)

Answer 5

x²-1=80

x²    =80+1

x^{2   =81}

^{=> x=9}