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Math C2 Algebra and Functions help

Hi, I dont know how to solve this question at all. Please do help

Given that -1 is a root of the equation 2x^3 - 5x^2 - 4x +3, find the two positive roots.

The answer in the book is 1/2 and 3.
I cant figure out how to do it please help
Reply 1
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Naika98
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Posted from TSR Mobile
1431163379930.jpg20.6KB
Original post by Naika98


The image you attached is correct? Strictly speaking it should be "x = -1 is a root of the equation 2x^3 - 5x^2 - 4x + 3 = 0"
Reply 3
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davros
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Original post by Naika98


...


Please don't post full solutions - it's against Forum rules :smile:
Reply 4
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davros
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Original post by Ugarit
Hi, I dont know how to solve this question at all. Please do help

Given that -1 is a root of the equation 2x^3 - 5x^2 - 4x +3, find the two positive roots.

The answer in the book is 1/2 and 3.
I cant figure out how to do it please help


You don't have an equation there - did you mean 2x^3 -5x^2 - 4x + 3 = 0?

Do you know what the factor theorem tells you?

Do you know how to do polynomial long division (or the equivalent by equating coefficients)?
Original post by davros
Please don't post full solutions - it's against Forum rules :smile:


Oh dear, for some reason I thought the person who posted the photo was OP :tongue: silly me
Reply 6
Avatar for Ugarit
Ugarit
OP
Original post by davros
You don't have an equation there - did you mean 2x^3 -5x^2 - 4x + 3 = 0?

Do you know what the factor theorem tells you?

Do you know how to do polynomial long division (or the equivalent by equating coefficients)?


In the book, the '=0' isnt written.
But Thank you so much
I did the long division, (divided 2x^3 -5x^2 - 4x + 3 by x+1) and then factorised, and my answers were correct :smile:

It completely slipped my mind that when they say -1 is a root of the equation, it means you can divide by x+1 with no remainder
Reply 7
Avatar for Ugarit
Ugarit
OP
Thanks for your help everyone!! :smile: Turns out all I needed to do was divide the equation by x+1 and then factorise. I feel silly for asking

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