The area of the rhombus formed by points of intersection of parabolas y=x^2 −b and y=−x^2 +b and their vertices is 54. Find b.

1 answer

If you draw out the graphs, you'll see that one of the diagonals of the rhombus is equal to 2b.

Further, you can obtain the points of intersection with the x-axis for the other diagonal.

For y = x^2 − b,
When y = 0, x = +√b/-√b

Hence, one diagonal of the rhombus is 2b, the other is 2√b

Area of a rhombus is given by:
(1/2) * Product of diagonals
= 0.5 * 2b * 2√b
= 2b√b = 54
=> b√b = 27
=> b = 3