a) Remember that the coordinates for any given point in the cartesian system have two components, one in the X axis and the secon one in the Y axis. (X,Y)
The coordinates for P and Q are:
P (b,a)
Q(d,e)
b) If you have the formula for the function, you'll se that to determine the value on the Y axis for a given value of X you have to replace that value in the formula. This means that Y= f(x).
In this example the value of Y for X=b is equal to a, so f(b)= a
c) For f(x)=e, you have to identify the value of x that croses to Y=e, in this grapfic that value is d
d) f(z)=c and f(x)=z
If you watch the graphic, c is in the y-axis, this means that the x value of its coordinate is zero. So z=0
Now for f(x)=z, this means that you have to find the value of x when the value of Y is zero. To determine this value you have to see where the function crosses the X-axis.
The function crosses the X-axis in point h, so when f(x)= z, x=h
e) If f(b)=-f(d) this means that both |b| and |d| are equal, you can express it as:
b=-d