If a is known to be a natural number and a is not equal to 0, then () A.A is reciprocal B.A and a are reciprocal C.A and a are reciprocal each other D. A and - A are reciprocal

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• 1. How much is ten and one-third minus four and one-fifth equal to forty-five and eleven eight minus (thirty and two fifths plus eight and eleven eight), etc What's ten and a third minus four and a fifth What's 45 and eight out of eleven minus (30 and two out of five plus eight and eight out of eleven) What's four and a quarter minus one and three sixteenth plus 0.75 There are three questions
• 2. The largest two odd divisors are () and the sum of all divisors is ()
• 3. Calculate 2 + 4 + 6 + ···· + 200 according to 1 + 2 + 3 + 4 + ··· + n = n (n + 1) / 2
• 4. Given the circle C: x2 + Y2 + DX + ey + 3 = 0, the circle C is symmetric about the straight line x + Y-1 = 0, the center of the circle is in the second quadrant, and the radius is 2. (I) solve the equation of the circle C; (II) find the equation of the straight line L whose origin is not known is tangent to the circle C, and the intercept on the x-axis and y-axis is equal
• 5. Given that a and B are opposite to each other, and ab is not equal to 0, CD is reciprocal to each other, find the value of a + B-Cd + a of 2013
• 6. A rope of 2 meters, the first minus two fifths, the second minus one third more than the first, a total of minus how many meters?
• 7. What are the divisors of the largest two odd numbers? What is the sum of all divisors?
• 8. Calculation; [(- 1 / 2) - (- 1 / 3) + (- 1 / 4)]
• 9. If the equation x2 + Y2 + DX + ey + F = 0 represents a circle with (2, - 4) as its center and 4 as its radius, then f=______ ．
• 10. Split term formula for summation of sequence
• 11. Let the sum of the first n terms of the sequence {an} be Sn, and 2An = Sn + 2n + 1 (n ∈ n *) (I) find A1, A2, A3; (II) prove that the sequence {an + 2} is an equal ratio sequence; (III) find the sum of the first n terms of the sequence {n · an} and TN
• 12. The circle X & sup2; + Y & sup2; + DX + ey + F = 0 is symmetric with respect to the line y = X A.D+E=0 B.D-E=0.C.D+F=0 D.D-F=O
• 13. Calculation of Y · y ^ n 1 - 2Y ^ n * y ^ 2 y ^ n-1y ^ 3 Can you explain every step of simplification? I don't know why it's 2Y ^ n * y ^ 2 y·y^n 1 -2y^n*y^2 y^n-1y^3
• 14. What are the conditions for the intersection of the circle x ＾ 2 + y ＾ 2 + DX + ey + F = 0 and the Y axis on both sides of the origin Detailed process, thank you
• 15. If the center of x ^ 2 + y ^ 2 + DX + ey + F = 0 (d ^ 2 + e ^ 2-4f > 0) is on the straight line x + y = 0, then the relation of D, e, f What does F have to do with them
• 16. In the equation x ^ 2 + y ^ 2 + DX + ey + F = 0, if d ^ 2 = e ^ 2 = 4f, then the position of the circle () A. The length of the chord obtained by cutting two axes is equal B. Tangent to both axes C. Away from two axes D. All of the above are possible
• 17. Excuse me, the general equation of this circle x + y + DX + ey + F = 0, why D + e-4f > 0? How is d + e-4f > 0 obtained?
• 18. What is the condition that "d square + e square - 4f > 0" is the equation x square + y square + DX + ey + F representing a circle?
• 19. The general equation of high school mathematics circle x ^ 2 + y ^ 2 + DX + ey + F = 0, f must be less than zero? What?
• 20. When d ^ 2 + e ^ 2-4f > 0, the quadratic equation x ^ 2 + y ^ 2 + DX + ey + F > 0 is called the equation of circle Is that right?