Under what circumstances does weda's law fail? RT OK = = in fact, I've got the answer I want, but it seems to be true many times? The plural is also true

The quadratic coefficient of the equation is equal to 0, or the equation of non real solution

If Detta is equal to zero, what law should Veda's law satisfy

x1+x2=2x1=-b/a
X1 · x2 = the square of X1 = C / A

Can we solve the value of X 1-x 2 by means of Weida's law

OK. (x1-x2) square = (x1 + x2) square - 4x1 * X2, in the root, finally judge the positive and negative

RELATED INFORMATIONS

1. The problem of quadratic term theorem The example in the book is to find the coefficient of X3 in the expansion of (x-1 / x) 9 I use the permutation and combination method C6 9 * (- 1) 6, and the result is 84 or - 84. Which step is wrong?
2. Remainder theorem If we divide the polynomials f (x) and G (x) by 2x ^ 2-3x-2, we can get the co expressions 2x + 3 and 4x-1 respectively, then the co expressions obtained by dividing f (x) - G (x) by 2x + 1 are
3. A problem of remainder theorem When f (x) = 2x ^ 3 + ax ^ 2 + BX + 3 divided by (x-1) (x + 2), the remainder is (2x + 1) a) f(1),f(-2) b) Two equations with a and B as unknowns are established c) Find the values of a and B
4. A problem of quadratic term theorem Known xy
5. How to prove the second Kepler theorem?
6. According to the law of conservation of mechanical energy The content of the law of conservation of mechanical energy says that only gravity (or spring force) does work. Does that mean that only spring force does work, and other forces can't?
7. The results are as follows: 1. The ball moves from point a to point B with the initial velocity V, and then returns automatically. The velocity of the ball passing through point a is () (the picture of this question is: A is on a horizontal track, moving for a period of time and then on an inclined plane, the height of the inclined plane is h, and the highest point is b) 4 options A radical (V ^ 2-4gh) B radical (4gh-v ^ 2) C radical (V ^ 2-2gh) D radical (2gh-v ^ 2)
8. The condition of the law of conservation of mechanical energy It is said in the book that the condition of conservation of mechanical energy is that the work is only done by gravity or elastic force. An object sliding on a smooth slope is only subject to gravity and supporting force, so its mechanical energy is conserved. However, if a crane lifts an object, its mechanical energy is not conserved, but it is only subject to gravity and tensile force. We all know that tensile force is also elastic force, so why? According to the book, the condition for the conservation of mechanical energy is that it is only affected by gravity or elastic force
9. As for the applicable conditions of the law of conservation of mechanical energy, the correct one in the following statement is () A. When there are other external forces, as long as the combined external force is zero, the mechanical energy is conserved. C. when there are other external forces, as long as the work of the resultant force of other forces is zero, the mechanical energy is conserved. D. when the projectile flies in the air without resistance, it is only affected by the heavy force, so the mechanical energy before and after the explosion is conserved
10. What are the conditions of the law of conservation of momentum, the law of conservation of kinetic energy and the law of conservation of mechanical energy, What's the difference?
11. What is substance? What is its theoretical significance? An introduction to the basic principles of Marxism
12. Veda's theorem (relation between root and coefficient) If X1 and X2 are two parts of the equation AX ^ 2 + BX + C = 0 1. Two positive roots 2. Two negative roots 3. One positive root and one negative root Both are bigger than one 5. One is bigger than one, and the other is smaller than one 6. One is bigger than 1, and the other is smaller than 0 7. Both of them are between 3 and 4
13. Theoretical yield coefficient
14. In △ ABC, it is known that ab = 102, a = 45 ° and the length of BC side is 202033 and 5 respectively, then the corresponding angle c is obtained
15. In the acute angle △ ABC, the opposite sides of angles a, B and C are a, B and C respectively. If AB + Ba = 6cosc, then the value of tanctana + tanctanb is______ ．
16. How to find the maximum value of X / (1 + x)
17. Urgent. High school mathematics! Let f (x) = 1 / 2x + SiNx, m be the maximum and n be the minimum on [0, π / 2], then the value of M + n is
18. In the triangle ABC, a, B and C are the opposite sides of three internal angles a, B and C respectively, and a, B and C are not equal to each other. Let a = 4, C = 3 and a = 2C. (1) find the value of COSC. (2) find the value of B I can do the first question (COSC = 2 / 3), but I can't do the second one
19. Given a + 2B + 3C = 20, a + 3B + 5C = 31, then the value of a + B + C is () A. 6B. 7C. 8D. 9
20. In △ ABC, if a ^ 4 + B ^ 4 + C ^ 4 = 2 (A & # 178; + B & # 178;) C & # 178;, then the degree of ∠ C is