Question 310918
If y = 4x – 3 and 0 < x < 3, then y is between 

a) -3 & 9 b) -2 & 10 c) 0 & 12 d) 1 & 5 e) 1 & 9
<pre><b>
The trick here is to build x into y, which is 4x - 3 
by multiplying all three sides of 

 0 < x < 3

by 4 and then subtracting 3 from all three sides.

Multiplying all three sides of 

 0 < x < 3

by 4 gives:

4*0 < 4*x < 4*3 

or

  0 < 4x < 12

Now subtracting 3 from all three sides of the above
gives:

 0 - 3 < 4x - 3 < 12 - 3

    -3 < 4x - 3 < 9

And since y = 4x - 3, we can substitute y for 4x - 3

      -3 < y < 9

and that says that y is between -3 and 9.  Therefore
the correct choice is a)

Edwin</pre>