Question

for which of following functions is graphof y = |f(x)| identical to graph of y = f(x)?

A. f(x) = 2x
B. f(x) = -2x
C. f(x) = 2x^2
D. f(x) = -2x^2

i real not get this.

Answer 1

has to be positive for all x
has to be an even function, same + or -
so
2 x^2

Answer 2

ok can u explain to me again that i still not get it.

Answer 3

|f(x)| is positive, but

2x can be negative
-2x can be negative

x^2 is always positive, so

-2x^2 is always negative.

The only choice which is always positive is 2x^2

so, |2x^2| = 2x^2