Selangor Trial 2025 Add Maths Paper 1, Question 5Quadratic Functions

Solved on video in English · Form 4, Quadratic Functions · 6:24 video

The question

(a)

(a) By using the table method, find the range of values of x for x² − 4x − 5 > 0.

(b)

(b) It is given that α and β are the roots of the quadratic equation 2x² + hx − 2 = 0. Form a quadratic equation with roots 1/(α + 1) and 1/(β + 1) in terms of h.

Selangor Trial 2025 Add Maths Paper 1, Question 5: the question as drawn in Eduly's video6:24

Part (a)

Step 1

Factorise: x² − 4x − 5 = (x − 5)(x + 1). So we need (x − 5)(x + 1) > 0.

Why this step

A sign slip here, like (x + 5)(x − 1), ruins the rest. Expand back to check the middle term is −4x.

5 more steps, each with the reason for it, in the full solution

Final answer

x < −1 or x > 5

Where students lose marks

Watch out: > 0 means the positive regions, x < −1 or x > 5, not −1 < x < 5. Use strict signs.

Part (b)

7 more steps, each with the reason for it, in the full solution

Final answer

hx² − (h − 4)x − 2 = 0 (or hx² + (4 − h)x − 2 = 0)

Where students lose marks

Watch out: αβ = −2/2 = −1, not −2, and finish by multiplying through by h to clear the fractions.

Watch every step of this question solved on video (6:24), with the reason behind each step and a box that checks your own answer.

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