Squared and Reciprocal R-form
Square the whole range, including zero if it occurs
Let . Over a full turn, . Squaring does not preserve that order: both endpoints give 25, while gives the minimum 0.
For a shifted square such as , first find . This interval contains zero, so the minimum square is 0; the larger endpoint magnitude is 7, so the maximum is 49.
Find the minimum and maximum of over a full turn.
Show worked answer
The expression inside the square ranges from 1 to 11. It stays positive, so its square increases with it.
Check whether the denominator can be zero
For , the denominator ranges from 1 to 11. Both are positive: the larger denominator gives the smaller reciprocal.
For , zero is excluded and values near zero produce arbitrarily large positive or negative outputs. The two parts of give or , not a single interval between those numbers.
Worked example
Find the minimum of 1/(2 + t)², where the expression is defined.
The denominator is largest when is largest. Since , its largest square is 49.
It occurs at . At the expression is undefined; approaching that value makes it arbitrarily large, so there is no finite maximum.
Find the range of over a full turn. Can its denominator be zero?
Show worked answer
The denominator ranges from 2 to 12, so it is never zero. Divide 2 by 12 for the minimum and by 2 for the maximum.
