IDNLearn.com is designed to help you find reliable answers to any question you have. Receive prompt and accurate responses to your questions from our community of knowledgeable professionals ready to assist you at any time.

If the zeros of the polynomial [tex]\( x^2 + p x + q \)[/tex] are double the value of the zeros of [tex]\( 2x^2 - 5x - 3 \)[/tex], find the values of [tex]\( p \)[/tex] and [tex]\( q \)[/tex].

[CBSE Board - 2012]


Sagot :

Let's solve this problem step-by-step.

1. Identify the given polynomial and find its zeroes:

Given polynomial is [tex]\(2x^2 - 5x - 3\)[/tex]. To find its zeroes, we solve the quadratic equation:
[tex]\[ 2x^2 - 5x - 3 = 0 \][/tex]

The zeroes of this polynomial are [tex]\( \alpha \)[/tex] and [tex]\( \beta \)[/tex], which are the roots of the equation.

2. Find the zeroes of [tex]\(2x^2 - 5x - 3\)[/tex]:

We have the zeroes:
[tex]\[ \alpha = -\frac{1}{2} \quad \text{and} \quad \beta = 3 \][/tex]

3. Determine the zeroes of the new polynomial:

It is given that the zeroes of the polynomial [tex]\(x^2 + px + q\)[/tex] are double the zeroes of [tex]\(2x^2 - 5x - 3\)[/tex]. Therefore, if the zeroes of [tex]\(2x^2 - 5x - 3\)[/tex] are [tex]\( \alpha \)[/tex] and [tex]\( \beta \)[/tex], then the zeroes of [tex]\(x^2 + px + q\)[/tex] are [tex]\(2\alpha\)[/tex] and [tex]\(2\beta\)[/tex].

That means:
[tex]\[ 2\alpha = 2 \times \left( -\frac{1}{2} \right) = -1 \quad \text{and} \quad 2\beta = 2 \times 3 = 6 \][/tex]

4. Find the sum and product of the zeroes for the new polynomial:

Let the zeroes of [tex]\(x^2 + px + q\)[/tex] be [tex]\(2\alpha\)[/tex] and [tex]\(2\beta\)[/tex]:
[tex]\[ \sum \text{of zeroes of } (x^2 + px + q) = 2\alpha + 2\beta = -1 + 6 = 5 \][/tex]
[tex]\[ \text{product of zeroes of } (x^2 + px + q) = 2\alpha \times 2\beta = (-1) \times 6 = -6 \][/tex]

5. Relate the zeroes to coefficients of the polynomial [tex]\(x^2 + px + q\)[/tex]:

- For a polynomial [tex]\(x^2 + px + q\)[/tex], the sum of the zeroes equals [tex]\(-p\)[/tex].
Therefore:
[tex]\[ -p = 5 \quad \Rightarrow \quad p = -5 \][/tex]

- The product of the zeroes equals [tex]\(q\)[/tex].
Therefore:
[tex]\[ q = -6 \][/tex]

Thus, the values of [tex]\(p\)[/tex] and [tex]\(q\)[/tex] for the polynomial [tex]\(x^2 + px + q\)[/tex] are:
[tex]\[ \boxed{p = -5 \quad \text{and} \quad q = -6} \][/tex]