joyrider wrote:Okay then...
Firstly, I don't understand what the steps are to make -x^2-2x+5 into
-(x+1-6^.5)(x+1+6^.5). The reason is because when I get to -(x+1)^2+6 I can't use the difference of two squares rule (the rule where a^2-b^2 = (a+b)(a-b)) as 6 isn't negative.
Secondly, I don't understand how to get 16x^2-y^2-4y-4 into (4x-y-2)(4x+y+2). One of my experiments brought me to this: 16x^2-y^2-4y-4 = (4x-y)(4x+y)-4y-4 = (4x-y+2)(4x+y-2)-4y, with the stray -4y at the end. In order to factor that all I used was the difference of two squares rule and I know that (4x-y+2)(4x+y-2) = 16x^2-y^2-4y-4 through expansion.
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