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9. Afla numarul necunoscut - RAPID!

j) 8x = 3,2(la puterea a 2 a)
l) 2,6x - 1 = 2,4(la puterea a 2 a)
n) 2,89 - 0,8x = 1,5(la puterea a 2 a)
-- Doar rezultatul este la puterea a doua


Răspuns :

Punctul j)

[tex]8x=3,2^2\\ 8x=10,24 \\ x=10,24 : 8\\ x=1,28[/tex]

Punctul l)

[tex]2,6x-1=2,4^2\\ 2,6x-1=5,76\\ 2,6x=6,76\\ x=6,76 : 2,6\\ x=2,6[/tex]

Punctul n)

[tex]2,89-0,8x=1,5^2\\ 2,89-0,8x=2,25\\ 0,8x=2,89-2,25\\ 0,8x=0,64\\ x=0,64 : 0,8\\ x=0,8[/tex]

[tex]\bf 3,2^2=3,2\cdot3,2=10,24\\ \\ \it j)\ \ 8x=3,2^2 \Rightarrow 8x=10,24\bigg|_{:8} \Rightarrow x=1,28\\ \\ \\ \ell )\ \ 2,6x-1=2,4^2\bigg|_{\cdot5} \Rightarrow 13x-5=5\cdot5,76 \Rightarrow 13x=5\cdot5,76+5 \Rightarrow \\ \\ \Rightarrow 12x=5(5,76+1) \Rightarrow 13x=5\cdot6,76\bigg|_{:13} \Rightarrow x=5\cdot0,52=2,6[/tex]