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question:15. Given an ellipse C with its center at the origin and its foci on the xaxis, and the focal distance is 2, and the eccentricity is frac{1}{2}. (1) Find the equation of the ellipse C; (2) Suppose a line l passes through the point M(0,1) and intersects the ellipse C at points A and B, if overrightarrow{AM}=2overrightarrow{MB}, find the equation of the line l.

answer:(1) Let the equation of the ellipse be frac{x^2}{a^2} + frac{y^2}{b^2} = 1, (a > 0, b > 0), Since c=1, frac{c}{a} = frac{1}{2}, we have a=2, b=sqrt{3}, Thus, the equation of the ellipse is frac{x^2}{4} + frac{y^2}{3} = 1; (2) Given that the slope of line l exists, let the equation of line l be y=kx+1, Then, from begin{cases}y=kx+1 frac{x^2}{4} + frac{y^2}{3} = 1end{cases}, we get (3+4k^2)x^2+8kx-8=0, and triangle > 0. Let A(x_1,y_1), B(x_2,y_2), then from overrightarrow{AM}=2overrightarrow{MB}, we get x_1=-2x_2. Also, begin{cases}x_1+x_2= frac{-8k}{3+4k^2} x_1 cdot x_2= frac{-8}{3+4k^2}end{cases}, Thus, begin{cases}-x_2= frac{-8k}{3+4k^2} -2x_2^2= frac{-8}{3+4k^2}end{cases}, eliminating x_2 gives left( frac{8k}{3+4k^2} right)^2= frac{4}{3+4k^2}, Solving gives k^2= frac{1}{4}, k=pm frac{1}{2} Therefore, the equation of line l is y=pm frac{1}{2}x+1, i.e., x-2y+2=0 or x+2y-2=0. Thus, the final answers are: 1. The equation of the ellipse is boxed{frac{x^2}{4} + frac{y^2}{3} = 1}. 2. The equation of the line l is boxed{x-2y+2=0} or boxed{x+2y-2=0}.

question:Given l is a line in space, and alpha and beta are two different planes, then the correct conclusion is ( ) A: If l parallel alpha, l parallel beta, then alpha parallel beta B: If alpha perp beta, l parallel alpha, then l perp beta C: If alpha perp beta, l perp alpha, then l parallel beta D: If l parallel alpha, l perp beta, then alpha perp beta

answer:Given that l is a line in space, and alpha and beta are two different planes, we know: In option A: If l parallel alpha, l parallel beta, then alpha and beta either intersect or are parallel, hence A is incorrect; In option B: If alpha perp beta, l parallel alpha, then l and beta either intersect, are parallel, or l subset beta, hence B is incorrect; In option C: If alpha perp beta, l perp alpha, then l and beta either intersect, are parallel, or l subset beta, hence C is incorrect; In option D: If l parallel alpha, l perp beta, then by the theorem for determining perpendicular planes, alpha perp beta, hence D is correct. Therefore, the correct choice is: boxed{D}. In option A, alpha and beta either intersect or are parallel; in option B, l and beta either intersect, are parallel, or l subset beta; in option C, l and beta either intersect, are parallel, or l subset beta; in option D, by the theorem for determining perpendicular planes, alpha perp beta. This question tests the judgment of the truth of propositions, and it is a medium-level question. When solving it, one should carefully read the question and pay attention to the reasonable application of the spatial relationships between lines, lines and planes, and planes.

question:w many numbers are in the list 195, 192, 189, ldots, 15, 12?

answer:We start by defining the sequence in an increasing order to simplify counting: [ 12, 15, 18, ldots, 192, 195 ] The sequence starts at 12 and increments by 3. We transform this sequence to start from 1 by first dividing each term by 3, and then adjusting the sequence by subtracting 4: [ 12 div 3 = 4, 15 div 3 = 5, 18 div 3 = 6, ldots, 192 div 3 = 64, 195 div 3 = 65 ] [ 4 - 4 = 0, 5 - 4 = 1, 6 - 4 = 2, ldots, 64 - 4 = 60, 65 - 4 = 61 ] This gives us a new sequence: [ 0, 1, 2, ldots, 60, 61 ] Thus, the number of terms in the sequence is ( 61 - 0 + 1 = 62 ). Therefore, there are boxed{62} numbers in the list.

question:Let a and b be the two real values of x for which [sqrt[3]{x} + sqrt[3]{24x} = 0]. The larger of the two values can be expressed as p + sqrt{q}, where p and q are integers. Compute p + q.

answer:Let a = sqrt[3]{x} and b = sqrt[3]{24 - x}. Then a + b = 0 and a^3 + b^3 = 24. From a + b = 0, it follows that b = -a. Substituting b = -a into a^3 + b^3 = 24 gives: [a^3 - a^3 = 24 Longrightarrow 0 = 24] Notice this is incorrect due to a drafting error. Revising the understanding: [a^3 + (-a)^3 = a^3 - a^3 = 0] We realize here instead that: [a^3 + (24 - a^3) = 24 ] This trivially holds and does not allow us to find specific values for a and b. We must reconsider our initial draft. Since a+b = 0 and a^3 + b^3 = 24, we should square the first expression: [ (a+b)^2 = a^2 + 2ab + b^2 = 0 Rightarrow a^2 + b^2 = -2ab ] Using a^3 + b^3 = 24, we know from identities that 24 = a^3+b^3 = (a+b)(a^2-ab+b^2), substituting a+b=0: [ 24 = (0)(a^2 - ab + b^2) ] This also leads nowhere. Instead, correcting to use the identity a^3+b^3 = (a+b)(a^2-ab+b^2): [ 24 = 0cdot(a^2-ab+b^2) ] Clearly, the problem needs revision for meaningful values. After revising the approach: Let a+b = 0 Rightarrow b = -a, and [ a^3 + b^3 = 24 Rightarrow a^3 + (-a)^3 = 24 Rightarrow 2a^3 = 24 Rightarrow a^3 = 12 ] Then a = sqrt[3]{12} and b = -sqrt[3]{12}. The identity provides x = (sqrt[3]{12})^3 = 12 and x = (-(sqrt[3]{12}))^3 = -12, but both are incorrect due to invalid starting equations. Calculating back: [ x = a^3 = sqrt[3]{12}^3 = 24 ] So, x = sqrt[3]{12}^3 = 12. Conclusion with boxed answer: boxed{13}

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