Question

Determinati numarul real x stiind ca numerele x+1, 1-x si 4 sunt in progresie aritmetica.

Answer 1

x+1, 1-x, 4. progresie aritmetică==>1-x=(x+1+4):2

(medie aritmetică)

$(1 - x) {}^{ \times 2} = \frac{x + 1 + 4}{2} \\ \\ \frac{2 - 2x}{2} = \frac{x + 1 + 4}{2} \\ 2 - 2x = x + 1 + 4 \\ - 2x - x = 5 - 2 \\ - 3x = 3 \\ x = \frac{3}{ - 3} \\ x = - 1$

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