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question:f P(a, b) is a point on the hyperbola x^2 4y^2 = m (m neq 0) and satisfies a 2b > 0 and a + 2b > 0, then the point must lie on the branch of the hyperbola that is A: on the right B: on the top C: on the right or top D: indeterminate
answer:Since P is a point on the hyperbola, by substituting into the hyperbola equation we get [a^2 - 4b^2 = (a-2b)(a+2b) = m.] Because a - 2b > 0 and a + 2b > 0, we can conclude m > 0. The center of the hyperbola is at the origin, and the transverse axis is parallel to the x-axis because the coefficients of y^2 and x^2 have opposite signs and m > 0. Also, since a - 2b > 0 and a + 2b > 0, it implies that 2a > 0 which means a > 0. Therefore, point P is on the right side of the y-axis and thus can only be on the right branch of the hyperbola. Hence, the correct answer is boxed{A}.
question:Given a2b+3=0, the value of the algebraic expression 5+2ba is __( ). A: 2 B: 4 C: 6 D: 8
answer:Since a-2b+3=0, it follows that a-2b=-3, therefore, the original expression =5-(a-2b) =5+3 =8. Hence, the correct choice is boxed{D}. From the given condition, we deduce that a-2b=-3, and then substitute it into the algebraic expression for calculation. This problem tests the evaluation of algebraic expressions, and it is important to pay attention to the application of the substitution method in solving it.
question:A line segment of constant length moves in a plane such that its ends slide along the sides of a right angle. What is the trajectory of the midpoint of this segment?
answer:1. **Identify Key Elements and Terminology**: Let O be the vertex of the given right angle, AB be the moving segment, and M be the midpoint of AB. We need to find the trajectory of point M as A and B slide along the axes forming the right angle at point O. 2. **Understanding the Geometry**: Consider the right-angled triangle formed by the axes and the segment AB. The hypotenuse of this triangle is the segment AB. 3. **Median from Vertex in Right-Angled Triangle**: Recall the property of a right-angled triangle: the median from the vertex at the right angle to the hypotenuse is equal to half the hypotenuse. This follows from the fact that the median to the hypotenuse of a right-angled triangle is equivalent to the radius of the circumcircle of the triangle, which is half the length of the hypotenuse. Therefore, the distance from vertex O to the midpoint M of AB is: [ OM = frac{1}{2} AB ] 4. **Trajectory of the Midpoint**: Since the length of AB is constant, the midpoint M is always a fixed distance from point O. Specifically, the distance OM = frac{1}{2} AB is constant. 5. **Recognizing the Path of the Midpoint**: The fixed distance implies that point M traces a circular path centered at O with a radius equal to frac{1}{2} AB. However, since A and B slide along the right-angle axes, point M will only trace out a quarter of this circle. 6. **Conclusion**: The trajectory of the midpoint M of the segment AB is a quarter circle with a radius of frac{1}{2} AB, centered at point O. [ boxed{text{Quarter of a circle}} ]
question:Determine the range of the real number a such that the proposition p: There exists x_0 in [0, frac{pi}{4}] such that sin(2x_0) + cos(2x_0) > a is a false statement.
answer:To establish that the proposition p is a false statement, we must demonstrate that for all x in [0, frac{pi}{4}], the inequality sin(2x) + cos(2x) leq a holds true. Given that the combination of a sine and a cosine function with the same argument can be expressed using the sine of a shifted angle, we find that begin{align*} sin(2x) + cos(2x) &= sqrt{2} sinleft(2x + frac{pi}{4}right) leq a. end{align*} To determine the boundary condition for a, consider the maximum of the sine function over the interval: begin{align*} 2x + frac{pi}{4} in left[frac{pi}{4}, frac{3pi}{4}right], end{align*} where the maximum value of sin is 1. For the original inequality to hold for all x in the given interval, we need begin{align*} frac{a}{sqrt{2}} geq 1, end{align*} which implies that a geq sqrt{2}. Therefore, the correct range of a, which makes the initial proposition a false one, is a geq sqrt{2}. begin{align*} boxed{D: a geq sqrt{2}} end{align*}