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- Thread starter Problem+Solve=Reason
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Can you factorise??? (or is this what you mean by factoring???)Problem+Solve=Reason said:

E.g. Could I give you [tex]x^2+5x+6[/tex] and you would end up with [tex](x+2)(x+3)[/tex]???

The Bob (2004 ©)

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HallsofIvy

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(Of course, when I saw "2 ways to execute a quadratic equation" my first thought was "firing squad and hanging"!)

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Sorry. My schools have always said it was factorising.HallsofIvy said:Yep, us colonials say "factoring" rather than "factorize"!

LoL. I know. There is an easy way and a way that allows you to do the easy way. :tongue2:HallsofIvy said:(Of course, when I saw "2 ways to execute a quadratic equation" my first thought was "firing squad and hanging"!)

The Bob (2004 ©)

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u should try factoring first, it's easier if it work, if not use the quadratic equation

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Can anyone explain why when you factorise and use the quadratic equation the answers have different signs?

Lets say for x^2 + 5x + 4

If i do it by factoring the answer would be (x+4)(x+1)

However, if done by the quadratic equation the answer would be (x-4)(x-1) which doesn't work when u multiply them out.

The signs are reversed.

Thanks alot! I need to explain this to my sis...Should I tell her to reverse her answers if she does it by the quadratic equation?

Yawie

Lets say for x^2 + 5x + 4

If i do it by factoring the answer would be (x+4)(x+1)

However, if done by the quadratic equation the answer would be (x-4)(x-1) which doesn't work when u multiply them out.

The signs are reversed.

Thanks alot! I need to explain this to my sis...Should I tell her to reverse her answers if she does it by the quadratic equation?

Yawie

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HallsofIvy

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Do you even KNOW what you mean by "the answer"??yawie said:Can anyone explain why when you factorise and use the quadratic equation the answers have different signs?

Lets say for x^2 + 5x + 4

If i do it by factoring the answer would be (x+4)(x+1)

However, if done by the quadratic equation the answer would be (x-4)(x-1) which doesn't work when u multiply them out.

The signs are reversed.

Thanks alot! I need to explain this to my sis...Should I tell her to reverse her answers if she does it by the quadratic equation?

Yawie

The correct "answer" to any question does NOT depend on which method you use to answer it!

What question are you trying to answer?

IF you are trying to answer the question, "What are the linear factors of

x

To use the "quadratic formula", you would convert to the EQUATION x

IF the question is "What are the roots of x

By "factoring", you determine that x

So: exactly WHAT problem are you trying to solve?

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but you answered the question....when you said x+4 = 0 is when you factor and when you use the quadratic equation you get x=-4....Now I know how to explain it to her....thanks!

I didn't realise the questions were differently phrased...

THanks!

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mathwonk

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x^2 + 5x + 25/4 = 25/4 -4 = 9/4. then take square roots of both sides to get

(x+5/2)^2 = 3/2. so x+5/2 = 3/2 or -3/2. so x = -5/2 + 3/2 = -2/2 = -1, or x = -5/2 - 3/2 = -8/2 = -4.

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ParabolaProblem+Solve=Reason said:

General form:

[tex]f(x)=ax^2+bx+c[/tex]

Quadratic Formula for Zeros:

[tex]x_1x_2=\frac{-b\pm\sqrt{(b^2)-(4ac)}}{2a}[/tex]

For Standard form

[tex]f(x)=a(x-h)^2+k[/tex]

Formula:

[tex]x_1x_2=h\pm\sqrt{\frac{-k}{a}}[/tex]

Just plug in the parameters.

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