Question 11671: PLEASE ANSWER ASAP!!!!
Points A and B are on a parabola y = 4x^2+ 7x -1 and the origin is the midpoint of AB.
***What is the length of AB?
THANK YOU!!!
Answer by khwang(438)   (Show Source):
You can put this solution on YOUR website! Let A = (xo,yo) ,B = (x1,y1),then their midpoint is
((xo+x1)/2,(yo+y1)/2) = (0,0).
So x1=-x0,y1=-yo.
Since A,B are both on the the parabola,
we have yo =  ...(1) and
-yo =  ...(2)
(1)+(2): 0 = 
So, xo = 1/2 or -1/2
and hence,yo = 4(1/4) - 7/2 - 1= -7/2
or yo = 7/2
Let O be the origin.
We see that the length of AB = 2 distance of OA
= 2
= 2 
= 
Kenny
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