Răspuns:
[tex]\bf lg \ 90 = 2a + 1[/tex]
Explicație pas cu pas:
[tex]lg \ 3 = a[/tex]
[tex]lg \ 90 = lg \ (9\cdot10) = lg \ 9+lg \ 10 =[/tex]
[tex]= lg \ 3^2+1=2 \cdot lg \ 3+1=2a+1[/tex]
Unde:
[tex]lg \ x = \log_{10}x[/tex]
q.e.d.
Formule utilizate:
[tex]\boldsymbol{\log_{a} x \cdot y = \log_{a} x + \log_{a} y}[/tex]
[tex]\boldsymbol{\red{\log_{a} a = 1} }[/tex]
