Question

If f(x) = −2[x]+ 8, what is f(−1.8)? 4 6 10 12

Answer 1

Functions whose graphs resemble sets of stairsteps are known as step functions. The most famous of the step functions is the greatest integer function, which is denoted by:

$f(x)=[x]$

which graph is shown in the Figure below. As you can see from the graph:

$if \ x=-1.8 \ then \ f(-1.8)=[-1.8]=-2$

Therefore:

$f(-1.8)=-2[-1.8]+8=-2(-2)+8=\boxed{12}$

So the right answer is 12

Answer 2

If you would like to calculate f(-1.8), you can do this using the following steps:

f(x) = -2 * x + 8
f(-1.8) = -2 * (-1.8) + 8 = 3.6 + 8 = 11.6

The correct result would be 11.6.