+82 The function f(x) < 0 when -2 < x < 1. Which of the following is true about the function |f(x) | ?
a) |f(x) | = - f(x) when -1 < x < 2
b) |f(x) | = f(x) when -1 < x < 2
c) |f(x) | = - f(x) when -2 < x < 1
d) |f(x) | = f(x) when -2 < x < 1
+240 Options a and b are eliminated because we don't know anything about f(x) when x is in range -1 < x < 2.
Looking at c and d, we try to see which one makes sense. Because we know in this range of -2 < x < 1, f(x) will be negative, we can rewrite c and d.
c) = |f(x)| = f(x) because the -1 * -1 = 1
d) |f(x)| = -f(x) since f(x) in range -2 < x < 1 is negative.
Therefore the answer is c).
