How many real numbers are roots of the polynomial x9−37x8−2x7+74x6+x4−37x3−2x2+74x?
Official solution
1. Given the polynomial: P(x)=x9−37x8−2x7+74x6+x4−37x3−2x2+74x We need to determine the number of real roots.
2. The polynomial can be factored as: P(x)=(x4−37x3−2x2+74x)(x5+1)
3. Further factorization of x4−37x3−2x2+74x: x4−37x3−2x2+74x=x(x3−37x2−2x+74)
4. The polynomial x3−2x can be factored as: x3−2x=x(x2−2)=x(x−2)(x+2)
5. Therefore, the factorization of the original polynomial becomes: P(x)=x(x−2)(x+2)(x−37)(x5+1)
6. The roots of x(x−2)(x+2)(x−37) are: x=0,±2,37 These are four distinct real roots.
7. The polynomial x5+1 can be factored using the sum of cubes: x5+1=(x+1)(x4−x3+x2−x+1) The factor x+1 has a real root: x=−1 The factor x4−x3+x2−x+1 has no real roots because its discriminant is negative, indicating no real solutions.
8. Combining all the real roots, we have: x=0,±2,37,−1
9. Therefore, the total number of real roots is: 5
Source: NuminaMath-1.5,
licensed Apache-2.0.
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