View Full Version : solving equations with greatest integer function
1. The problem statement, all variables and given/known data
I can't find a step by step explanation for solving these types of equations
eg.
99 = [2x+1]/3
2. Relevant equations
eg.
99 = [2x+1]/3
or
48 = 4[2x/3]
How do you handle the multipliers iand constants inside the brackets?
thx
[b]3. The attempt at a solution[b]
Think about how the greatest integer function works. For example,
\lfloor 3.2 \rfloor = \lfloor 3.582 \rfloor = 3
and in fact, if 3 \le x < 4 it is true that
\lfloor x \rfloor = 3
So, if you know that
\frac{\lfloor 2x+1\rfloor}{3} = 99
you also know that
\lfloor 2x+1 \rfloor = 297
(the 3 in the denominator is not in the function). What does the final
statement above tell you about how large 2x + 1 must be?
Think about how the greatest integer function works. For example,
\lfloor 3.2 \rfloor = \lfloor 3.582 \rfloor = 3
and in fact, if 3 \le x < 4 it is true that
\lfloor x \rfloor = 3
So, if you know that
\frac{\lfloor 2x+1\rfloor}{3} = 99
you also know that
\lfloor 2x+1 \rfloor = 297
(the 3 in the denominator is not in the function). What does the final
statement above tell you about how large 2x + 1 must be?
--------------------
so 297 <= 2x+1 < 298
296 <=2x and 2x < 297
148 <=x and x < 148.5
Did I get it?
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