What are the definitions of the focus and directrix?

... b2​=a(x+2ab​)2 ... −(b2 − 4ac) = 4ac − b2. The formula for h has a denominator of 2a; double ... s = (-b – [b2 – 4ac])/2a. 1. Add them: r + s = (-b + -b)/2a = -b/a. 2. Multiply them: rs = ([-b]2 – [b2 – 4ac])/4a2 = c/a. back. However, we know there must be another independent solution. It's not obvious what that might be, but let's make the educated guess y(t) = C2teλ1t. Jun 20, 2014 ... ... (b2-4ac ≥ 0) ⇒ (x = {-b-√{b2-4ac}}/{2a}) \lor (x = {-b+√{b2-4ac}}/{2a}). Please write complete proofs in each subquestion, without ... Jun 4, 2014 ... 3 Answers 3 ... Δ=b2−4ac>0 means that the equation has two real solutions. Δ=b2−4ac<0 means that the equation has no real solutions, but two ... given the nature of the roots, to find the condition that makes this happen. Find the nature of the roots of 9x² +24x+16=0. a = 9 b=24 c = 16 b2-4ac ... Jun 4, 2020 ... I wish I could use b^2-4ac>0 to check whether the people are real or not. Jun 12, 2017 ... The question asks whether entire parabola is below x-axis. This will happen if discriminant is negative AND the parabola opens downward. ... 2 + bxy + cy 2 of discriminant b 2 - 4ac = - d we can associate an ideal of norm a. Then the quadratic form associated to d with respect to this basis is Q ... b2 – 4ac < 0. No real roots. 4. b2 – 4ac = 32- 4x1x(-2) = 9 +8 = 17. b2 ... If b2 – 4ac < 0 , the line does not touch the curve. It is not a tangent. If ...