I'm having problems with this function: y= 8(-x)^2+2(-x)
We are supposed to compare it to y= x^2+2x using transformations. I found its' vertex form: y=(x+1)^2-1 but I can seem to figure out how to turn the function above into its vertex form.
I figured turning them both into their vertex forms would make the comparison easier. I tried doing this:
1. y=8(-x)^2+2(-x)
2. y=-8x^2-2x Distributed the (-)...
3. y=-2(4x^2x+1)-1 Completed the square....
4. y=-2(4x^2x+1)+2 Can't factor....
But this doesn't match 8(-x)^2+2(-x) on the graphing calculator, so that isn't the vertex form... Am I not supposed to touch the x's? Or should I do this: -2x(4x+1)?
Can anyone explain my mistake and show me what I should do please? I've done the other problems like this but this is the odd-ball, and I've stared so long at it the answer could bite me and I wouldn't know it. I appreciate any help and thanks for reading this thread!
Thanks~!
We are supposed to compare it to y= x^2+2x using transformations. I found its' vertex form: y=(x+1)^2-1 but I can seem to figure out how to turn the function above into its vertex form.
I figured turning them both into their vertex forms would make the comparison easier. I tried doing this:
1. y=8(-x)^2+2(-x)
2. y=-8x^2-2x Distributed the (-)...
3. y=-2(4x^2x+1)-1 Completed the square....
4. y=-2(4x^2x+1)+2 Can't factor....
But this doesn't match 8(-x)^2+2(-x) on the graphing calculator, so that isn't the vertex form... Am I not supposed to touch the x's? Or should I do this: -2x(4x+1)?
Can anyone explain my mistake and show me what I should do please? I've done the other problems like this but this is the odd-ball, and I've stared so long at it the answer could bite me and I wouldn't know it. I appreciate any help and thanks for reading this thread!
Thanks~!
