Question

Tìm x biết:

a) 5^x+5^x+2=650

b)3^x-1+5 x 3^x-1 = 162

Answer 1

a) 5^X+5^X+2=650

=>5^X.1+5^X.5²=650

=>5^X.(1+5²)=650

=>5^X.26=650

=>5^x=650:26

=>5^X=25

=>5^X=5²

=>X=2

b) 3^X-1+5.3^X-1=162

=>3^X-1.1+5.3^X-1=162

=>3^X-1.(1+5)=162

=>3^X-1.6=162

=>3^X-1=162:6

=>3^X-1=27

=>3^X-1=3³

=>3^X=3³⁺¹

=>3^X=3⁴

=>X=4

Answer 2

=> \(5^x+5^x.5^2=650\)

\(5^x\left(1+5^2\right)=650\Leftrightarrow5^x.26=650\)

\(\Leftrightarrow5^x=25;x=2\)