Question

9. if P, Q are the roots of a q.e
ax2+bx+c=0 Then P/Q+Q/P =
1.b2+ 2ac7 a 2
2.b2-2аc / a2
3.b2+ 2ac/ac
4.b2 - 2ac / ac​

Answer 1

Quadratic Equation Formula

The solution or roots of a quadratic equation are given by the quadratic formula:

(α, β) = [-b ± √(b2 – 4ac)]/2ac

Formulas for Solving Quadratic Equations

1. The roots of the quadratic equation: x = (-b ± √D)/2a, where D = b2 – 4ac

2. Nature of roots:

D > 0, roots are real and distinct (unequal)

D = 0, roots are real and equal (coincident)

D < 0, roots are imaginary and unequal

3. The roots (α + iβ), (α – iβ) are the conjugate pair of each other.

4. Sum and Product of roots: If α and β are the roots of a quadratic equation, then

S = α+β= -b/a = coefficient of x/coefficient of x2

P = αβ = c/a = constant term/coefficient of x2

5. Quadratic equation in the form of roots: x2 – (α+β)x + (αβ) = 0

6. The quadratic equations a1x2 + b1x + c1 = 0 and a2x2 + b2x + c2 = 0 have;

One common root if (b1c2 – b2c1)/(c1a2 – c2a1) = (c1a2 – c2a1)/(a1b2 – a2b1)

Both roots common if a1/a2 = b1/b2 = c1/c2

7. In quadratic equation ax2 + bx + c = 0 or [(x + b/2a)2 – D/4a2]

If a > 0, minimum value = 4ac – b2/4a at x = -b/2a.

If a < 0, maximum value 4ac – b2/4a at x= -b/2a.

8. If α, β, γ are roots of cubic equation ax3 + bx2 + cx + d = 0, then, α + β + γ = -b/a, αβ + βγ + λα = c/a, and αβγ = -d/a

9. A quadratic equation becomes an identity (a, b, c = 0) if the equation is satisfied by more than two numbers i.e. having more than two roots or solutions either real or complex.