If alpha and beta are the zeros of the polynomial 2x^2-5x+7, then find...
If alpha and beta are the zeros of the polynomial 2x^2-5x+7, then find...
Answer:
Given:
Zeros of 2x^2-5x+7 are alpha and beta.
We need to find the polynomial whose zeros are 2alpha+3beta and 3alpha+2beta.
Explanation:
We know that if alpha and beta are the roots of the quadratic equation ax^2+bx+c=0, then the equation can be written in the form of a(x-alpha)(x-beta)=0.
Let's find the equation whose roots are alpha and beta.
The given quadratic equation is 2x^2-5x+7=0.
Using the quadratic formula, we can find the roots of this equation as:
alpha = (5+sqrt(11))/4
beta = (5-sqrt(11))/4
Now, we can write the equation in the form of a(x-alpha)(x-beta)=0 as:
2(x-alpha)(x-beta)=0
Expanding this equation, we get:
2x^2-(2alpha+2beta)x+2alpha*beta=0
Simplifying, we get:
2x^2-5x+7=0
Therefore, the equation whose roots are alpha and beta is 2x^2-5x+7=0.
Now, let's find the equation whose roots are 2alpha+3beta and 3alpha+2beta.
Let's assume that the equation is of the form ax^2+bx+c=0.
Using the sum and product of roots formula, we can find the values of b and c as:
b = -a(2alpha+3beta+3alpha+2beta) = -5a(alpha+beta)
c = a(2alpha+3beta)(3alpha+2beta) = 6a(alpha*beta)
We know that the equation whose roots are alpha and beta is 2x^2-5x+7=0. Therefore, alpha*beta = 7/2 and alpha+beta = 5/2.
Substituting these values in the expressions of b and c, we get:
b = -5a(5/2) = -25a/2
c = 6a(2alpha+3beta)(3alpha+2beta) = 6a(6alpha^2+13alpha*beta+4beta^2)
Substituting the values of alpha and beta, we get:
c = 6a(6[(5+sqrt(11))/4]^2+13[(5+sqrt(11))/4][(5-sqrt(11))/4]+4[(5-sqrt(11))/4]^2)
Simplifying, we get:
c = 153a/8
Therefore, the equation whose roots are 2alpha+3beta and 3alpha+2beta is:
ax^2-25ax/2+153a/8=0
Simplifying, we get:
2x^2-25x+153=0
Thus, the polynomial whose zeros are 2alpha+3beta and 3alpha+2beta is 2x^2-25x+153.
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