For what value of k, the zeroes of a quadratic polynomial p(x)=2x²+9x+...
Introduction:
A quadratic polynomial is an expression of the form ax² + bx + c, where a, b, and c are constants. The zeroes of a quadratic polynomial are the values of x that make the polynomial equal to zero. In this problem, we are given a quadratic polynomial and we need to find the value of k such that the zeroes of the polynomial are negative reciprocals of each other.
Method:
To find the zeroes of the given quadratic polynomial, we can use the quadratic formula. The quadratic formula states that the zeroes of a quadratic polynomial ax² + bx + c are given by:
x = (-b ± √(b² - 4ac)) / 2a
If the zeroes of the polynomial are negative reciprocals of each other, then we can write:
x₁ = -1/x₂
Substituting this into the quadratic formula, we get:
-1/x₂ = (-b ± √(b² - 4ac)) / 2a
Multiplying both sides by x₂, we get:
-1 = (-b ± √(b² - 4ac))x₂ / 2a
Solving for x₂, we get:
x₂ = (-2a) / (-b ± √(b² - 4ac))
Since we want the zeroes of the polynomial to be negative reciprocals of each other, we can set x₁ = -1/x₂ and solve for k.
Solution:
The given quadratic polynomial is:
p(x) = 2x² + 9x (k - 2k + 1)
Expanding the polynomial, we get:
p(x) = 2x² + 9x (k - 2k + 1)
= 2x² + 9x (1 - k)
The discriminant of the quadratic formula is:
b² - 4ac = (9(1-k))² - 4(2)(0)
Simplifying, we get:
b² - 4ac = 81(1 - 2k)
Since we want the zeroes of the polynomial to be negative reciprocals of each other, we can set x₁ = -1/x₂ and solve for k. Substituting the values for the zeroes from the quadratic formula, we get:
x₁ = (-9 ± √(81(1 - 2k))) / 4
x₂ = (-2) / (-9 ± √(81(1 - 2k)))
Setting x₁ = -1/x₂ and simplifying, we get:
(9 ± √(81(1 - 2k))) / 2 = -2 / x₂
Multiplying both sides by x₂ and simplifying, we get:
(9 ± √(81(1 - 2k)))x₂ = -4
Substituting the value of x₂ from the quadratic formula, we get:
(9 ± √(81(1 - 2k))) (-9 ± √(81(1 - 2k))) = -8(1 - k)
Simplifying, we get:
81(1 - 2k) - 81(1 - 2k) ± 18√(81(1 - 2k)) =
For what value of k, the zeroes of a quadratic polynomial p(x)=2x²+9x+...
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