Senior Secondary (HKDSE) · Mathematics

Quadratic equations in one unknown : Practice Questions

5 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on Quadratic equations in one unknown .

10 questions23 marksFree, no account
Question 1
1 mark

Find the nature of the roots of the quadratic equation $$3x^2 - 4x + 2 = 0$$.

Question 2
1 mark

If one root of the quadratic equation \(5x^2 - 12x + k = 0\) is twice the other, find the value of \(k\).

Question 3
1 mark

If the roots of the quadratic equation \(x^2 - (2m+1)x + m^2 - 1 = 0\) are real and one root is twice the other, find the possible value(s) of \(m\).

Question 4
1 mark

Let \(\alpha\) and \(\beta\) be the roots of the quadratic equation \(x^2 - 5x + k = 0\) . If the sum of the squares of the roots is 13, i.e., \(\alpha^2 + \beta^2 = 13\) , find the value of the constant \(k\) .

Question 5
1 mark

If one root of the quadratic equation \(2x^2 - 7x + k = 0\) is twice the other, find the value of \(k\).

Question 6
3 marks

Form a quadratic equation in \(x\) with integer coefficients whose roots are 5 and -2.

Write your answer out first, then check it against the worked solution.

Question 7
4 marks

If \(\alpha\) and \(\beta\) are the roots of the quadratic equation \(x^2 - 6x + (k+3) = 0\), and it is given that \(\alpha^2 + \beta^2 = 20\), find the value of the constant \(k\).

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Question 8
5 marks

Find the range of values of $$k$$ such that the straight line $$y = x + k$$ does not intersect the parabola $$y = x^2 - x + 2$$.

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Question 9
3 marks

Let $$\alpha$$ and $$\beta$$ be the roots of the quadratic equation $$2x^2 - 6x + 5 = 0$$.

(a) Find the sum of the roots, $$\alpha + \beta$$.

(b) Find the product of the roots, $$\alpha \beta$$.

(c) Hence, find the value of $$\frac{1}{\alpha} + \frac{1}{\beta}$$.

Write your answer out first, then check it against the worked solution.

Question 10
3 marks

Consider the quadratic equation $$3x^2 - 6x + m = 0$$.

(a) Find the value of $$m$$ if the equation has exactly one real root.

(b) For the value of $$m$$ found in part (a), find this real root.

Write your answer out first, then check it against the worked solution.

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