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Correct answer: 2
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We need the number of real solutions of
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Substitute Since for all real , we have .
Then the equation becomes
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Observe that the polynomial is palindromic: coefficients are . Divide by (valid since ):
Rearranging,
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Let Then
So the equation becomes i.e.
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Solve for :
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Since , we know Therefore only is possible, because is not allowed.
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Now solve Multiplying by :
For the number of positive roots in , check discriminant:
Compute:
=\frac{22+2\sqrt{21}}{4} =\frac{11+\sqrt{21}}{2}.$$ Hence $$\Delta=\frac{11+\sqrt{21}}{2}-4 =\frac{3+\sqrt{21}}{2}>0.$$ So there are two distinct real roots in $t$. Also their product is $1>0$ and sum is positive, hence both roots are positive. -
Since is a one-to-one correspondence between and , each positive root of gives exactly one real .
Therefore, the curve cuts the -axis at 2 points.
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Comparison with stored answer: Stored correct answer = . Our derived answer also = .
Hence the number of points where the curve cuts the -axis is
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