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- Thread starter thomas49th
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- #2

cristo

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For (a) I got x = [tex]\sqrt{-11}[/tex] which you cant do as you cant square root a negitive number, I cant help but feel im wrong

Well, for that reason I would say that Bill is wrong; not you!

- #3

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x² + (2x-2)(2x-2) = 25

5x² -8x -21 = 0

am I doing the right thing so far. When I used the quadratic formula I got a decimal number, not a whole number and the question doesn't say anything about rounding to a degree of accuracy so I presume the answer is whole numbers

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arildno

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That is you have the two solutions:

[tex]x=\frac{-(-8)\pm\sqrt{(-8)^{2}-4*5*(-21)}}{2*5}=\frac{8\pm\sqrt{484}}{10}=\frac{8\pm{22}}{10}[/tex]

As it happens, you get rational solutions here, otherwise, the exact solutions would involve square root symbols explicitly.

- #5

cristo

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x² + (2x-2)(2x-2) = 25

5x² -8x -21 = 0

am I doing the right thing so far. When I used the quadratic formula I got a decimal number, not a whole number and the question doesn't say anything about rounding to a degree of accuracy so I presume the answer is whole numbers

What do you get when you solve this quadratic equation? The answer does not necessarily have to be a whole number, especially if it is only a short decimal. The solution to this equation is such that it can easily be written exactly.

- #6

HallsofIvy

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Or, to put it another way,

5x^{2}- 8x+ 21= (5x+ 7)(x- 3)= 0

5x

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- #8

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anyway the answer:

x = -7 or 3

y = -16 or 4

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arildno

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Eeeh??

Whatever are you talking about?

Whatever are you talking about?

- #10

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However im concerned that -16² + -7² dont equal 25

- #11

HallsofIvy

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[tex]x=\frac{-(-8)\pm\sqrt{(-8)^{2}-4*5*(-21)}}{2*5}=\frac{8\pm\sqrt{484}}{10}=\frac{8\pm{22 }}{10}[/tex]

and I told you that 5x

How could you possibly get "x = -7 or 3" from that?

- #12

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(8 + 22)/10 = 3

(8-22)/10 =**1.4**

woops

EDIT: Making y 4 or 4.8

(8-22)/10 =

woops

EDIT: Making y 4 or 4.8

- #13

HallsofIvy

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Well, I would have said 7/5 but but I grew up BC (before calculators).

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arildno

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Actually, I would say -7/5..

- #15

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8+22 = 30/10 =

8-22 = -14/10 =

feed that into the equation y = 2(x) - 2

2(3) - 2 = 6- 2 =

2(-1.4) - 2 = -2.8-2 =

I would think that must be right?

- #16

HallsofIvy

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