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March 15th, 2015, 10:49 AM   #1
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Question simplify

y= -4(x-1+√2) (x-1-√2)

I got y= -4(x-1)^2-2

In the answer key it says y= -4(x^2-2x-1)

who is right and please show why

Last edited by rrosa522; March 15th, 2015 at 11:18 AM.
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March 15th, 2015, 11:12 AM   #2
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Did you mean y = -4(x - 1 + √2) (x - 1 - √2)?

In that case, y = -4((x - 1)² - 2) = -4(x² - 2x - 1).
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March 16th, 2015, 09:16 PM   #3
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y=-4(x-1+√2)(x-1-√2)
y=(-4x+4-4√2)(x-1-√2)
y=(-4x²+4x+4√2x+4x-4-4√2-4√2x+4√2+4)
y=(-4x²+8x)
y=-4x(x+2)
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March 17th, 2015, 04:46 AM   #4
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Quote:
Originally Posted by TAMI EVAZ View Post
y=-4(x-1+√2)(x-1-√2)
y=(-4x+4-4√2)(x-1-√2)
y=(-4x²+4x+4√2x+4x-4-4√2-4√2x+4√2+4)
y=(-4x²+8x)
y=-4x(x+2)
Last term of the expansion in line three should be 8.
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March 17th, 2015, 07:05 PM   #5
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Quote:
Originally Posted by rrosa522 View Post
y= -4(x-1+√2) (x-1-√2)

I got y= -4(x-1)^2-2

In the answer key it says y= -4(x^2-2x-1)

who is right and please show why
(x- 1)^2= x^2-2x+ 1 so what is (x- 1)^2- 2?
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March 17th, 2015, 08:00 PM   #6
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Quote:
Originally Posted by rrosa522 View Post
y= -4(x-1+√2) (x-1-√2)

I got y= -4(x-1)^2-2

In the answer key it says y= -4(x^2-2x-1)

who is right and please show why
The answer key is right. Your mistake was you didn't put brackets after the expansion. You should get y = -4((x-1)^2-2) instead of y = -4(x-1)^2-2.
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