How many real solutions has the following equation with respect to X? | ||||
(X6 + π)·(5X + 1)·(X + 2)2·(X3 1) = 0 | ||||
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(X6 + π)·(5X + 1)·(X + 2)2·(X3 1) = 0 when 5X+1=0 or X+2=0 o X3-1=0 (X6+π never is 0). So -1/5, −2 and 1 are the only (real) numbers which, substituted for x, make the equation true. The correct answer is "3 solutions".
The solutions can also be found with WolframAlpha by introducing:
solve (x^6+pi)*(5*x+1)*(x+2)^2*(x^3-1) = 0 for x real
Note.
It is not true that every polynomial eq. of degree N has N solutions!!! x100=0 è is true only for x=0;
in some particular mathematical areas, to address some questions
(eg specify how close to the solution the curve y=
"squashes" on the x axis),
it is useful to introduce the concept of multiplicity, and to say that, e.g., for this equation, 0 is a solution of multiplicity 100
(we repeat: it would be an enormous nonsense, especially in teaching, to say that it has 100 coincident solutions: 100 ≠ 1!).
Note also that the formulation of the answer A is incorrect:
the Ruffini-Abel theorem does not state that for the polynomial equations in x
In a test submitted to about forty graduates in scientific faculties (in 2000) the question had only 38% of correct answers. 19% of graduates chose "12 solutions", 16% chose "4 solutions". 27% preferred not to respond.