Question

Para que a média aritmética de X/2,X/3 e X/4 seja maior que 1/5, quanto deve valer X?

A) X+1/-3 + X+2/5 > X+3/-4 - 1/10

B) X/3 + X-1/7 + X ≤ X-2/5 - X-3/4

C) 3 < X/5 + X/2 + X/4 - 1/20

D) -1 > X/2 + X/3 - X/4 + X/5 - 1/6

Answer 1

$\frac{\frac{x}{2}+\frac{x}{3}+\frac{x}{4}}{3}\ \textgreater \ \frac{1}{5}\\ \\ \frac{x}{2}+\frac{x}{3}+\frac{x}{4}\ \textgreater \ \frac{3}{5}\\ \\ \frac{13x}{12}\ \textgreater \ \frac{3}{5}\\ \\ 13x\ \textgreater \ \frac{36}{5}\\ \\ x\ \textgreater \ \frac{36}{65}$