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secondary 3 | A Maths
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J
J

secondary 3 chevron_right A Maths chevron_right Singapore

Hi. Pls help me with this qn.
Tia

Date Posted: 3 years ago
Views: 176

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Eric Nicholas K
Eric Nicholas K's answer
5997 answers (Tutor Details)
1st
Since the coefficient of x3 is -1, the shape of the graph is as such. This is one way we can draw the graph.
J
J
3 years ago
Thank you
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Eric Nicholas K
Eric Nicholas K's answer
5997 answers (Tutor Details)
One possible graph, along with its equation. One of the roots must be a repeated root, and in my this case I let x = -2 be the repeated root so that

f(x) = - (x + 2)² (x - 3)

The negative sign in front is to reflect the fact that the coefficient of x³ is -1.

When divided by x + 1, by the Remainder Theorem, the remainder is f (-1)
= - (-1 + 2)² (-1 - 3)
= - (1) (-4)
= 4

I will do a similar version for the other case.
J
J
3 years ago
Rachel you can see the repeated root part as though as it's like the usual quadratic graph where the discriminant = 0 (real and equal/repeated roots). It only intersects the x/axis at 1 point.

This helps you to know which turning point of the graph should touch the x-axis
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Eric Nicholas K
Eric Nicholas K's answer
5997 answers (Tutor Details)
The other possible graph, along with its equation. One of the roots must be a repeated root, and in my this case I let x = 3 be the repeated root so that

f(x) = - (x + 2) (x - 3)²

The negative sign in front is to reflect the fact that the coefficient of x³ is -1.

When divided by x + 1, by the Remainder Theorem, the remainder is f (-1)
= - (-1 + 2) (-1 - 3)²
= - (1) (16)
= - 16
Eric Nicholas K
Eric Nicholas K
3 years ago
Rachel, let me know if you need more explanation.