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 March 15th, 2015, 10:49 AM #1 Newbie   Joined: Feb 2015 From: canada Posts: 10 Thanks: 0 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.
 March 15th, 2015, 11:12 AM #2 Global Moderator   Joined: Dec 2006 Posts: 20,931 Thanks: 2205 Did you mean y = -4(x - 1 + √2) (x - 1 - √2)? In that case, y = -4((x - 1)² - 2) = -4(x² - 2x - 1).
 March 16th, 2015, 09:16 PM #3 Newbie   Joined: Mar 2015 From: sri lanka Posts: 2 Thanks: 0 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)
March 17th, 2015, 04:46 AM   #4
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 Originally Posted by TAMI EVAZ 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.

March 17th, 2015, 07:05 PM   #5
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Quote:
 Originally Posted by rrosa522 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?

March 17th, 2015, 08:00 PM   #6
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Quote:
 Originally Posted by rrosa522 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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