Răspuns :
[tex] {7}^{x} + {7}^{x + 2} = 2450 \\ {7}^{x} (1 + {7}^{2} ) = 2450 \\ 50 \times {7}^{x} = 2450 \\ {7}^{x} = 49[/tex]
De aici se deduce clar ca x = 2, dar evident ca se poate demonstra:
[tex] {7}^{x} = 49 \\ {7}^{x} = {7}^{2} [/tex]
Cand bazele sunt egale, comparam exponentii
=> x = 2
7^x + 7^(x+2) = 2 450
7^x + 7^x × 7^2 = 2 450
7^x × (1 + 7^2) = 2 450
7^x × 50 = 2 450
7^x = 2 450 : 50
7^x = 49
7^x = 7^2
x = 2
_____
7^x + 7^x × 7^2 = 2 450
7^x × (1 + 7^2) = 2 450
7^x × 50 = 2 450
7^x = 2 450 : 50
7^x = 49
7^x = 7^2
x = 2
_____