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3la putereax+3laputereax-1+3laputereax-2+3laputereax-3=40

Răspuns :

3la putereax+3laputereax-1+3laputereax-2+3laputereax-3=40

3ˣ+3ˣ⁻¹+3ˣ⁻²+3ˣ⁻³=40

3ˣ+3ˣ:3¹+3ˣ:3²+3ˣ:3³=40 (aducem la acelasi numitor respectiv 27

27x 3ˣ+9x3ˣ+3x3ˣ+3ˣ=40x27

3ˣ(27+9+3+1)=40 x 27

3ˣ x 40=27x40

3ˣ = 27

x = 3

deoarece 3³=27