UNO High School Problem of the Week Competition
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Problem 20
Find all real roots of
f
if
f
(x
1/9
) = x
2
- 3x -4.
Solution
Answer: 4
1/9
and -1
Observe that
f
(x
1/9
) = (x -4)(x+1). If f = 0, then x = 4 or x = -1 and both
f
(4
1/9
) and
f
(-1) = 0.
