HI, I am teaching ,myself algebra and eventually calculus.
I am doing great with expanding, but I have an issue with one questions; which is basically finding the area of a shaded area, when a cube inside is taking up some space.
So, the large rectangle had the formula (x+7) * (3x-y+4)
Which I was able to expand to:
3x^2-xy+4x+21x-7y+28
If the square inside has the area (x-2)2 then the formula would be:
3x^2-xy+4x+21x-7y+28 -(x-2)^2
its the -(x-2)^2 that is causing me an issue.
I can not for the life in me understand why -X^2+2x+2x-4 is the correct answer for -(x-2)^2 expansion. As in my head I am doing this
-(x-2)^2 = -1*(x-2)* -1*(x-2) = -(-x+2) * (-x+2) which I expand as X^2 -4x +4
So I guess what I should be doing is expanding -(x-2)*(x-2) which could give
My question is; how does -(x-2)^2 become -X^2+4x-4; where is my thought process betraying me?
With KR,
James
I am doing great with expanding, but I have an issue with one questions; which is basically finding the area of a shaded area, when a cube inside is taking up some space.
So, the large rectangle had the formula (x+7) * (3x-y+4)
Which I was able to expand to:
3x^2-xy+4x+21x-7y+28
If the square inside has the area (x-2)2 then the formula would be:
3x^2-xy+4x+21x-7y+28 -(x-2)^2
its the -(x-2)^2 that is causing me an issue.
I can not for the life in me understand why -X^2+2x+2x-4 is the correct answer for -(x-2)^2 expansion. As in my head I am doing this
-(x-2)^2 = -1*(x-2)* -1*(x-2) = -(-x+2) * (-x+2) which I expand as X^2 -4x +4
So I guess what I should be doing is expanding -(x-2)*(x-2) which could give
My question is; how does -(x-2)^2 become -X^2+4x-4; where is my thought process betraying me?
With KR,
James