# Find the area included between the parabolas y^2 = 4ax and x^2 = 4by.

10 views

closed

Find the area included between the parabolas y2 = 4ax and x2 = 4by.

+1 vote
by (22.8k points)
selected by

To find area enclosed by

Y2 = 4ax

y = $2\sqrt{ax}$ ....(i)

And x2 = 4by

y = $\frac{x^2}{4b}$ .....(ii)

On solving the equation (i) and (ii),

$\frac{x^4}{16b^2}$ = 4ax

Or, x4 – 64ab2x = 0

Or, x(x3 – 64ab2) = 0

Or, x = 0 and x = $4\sqrt[n]{ab^2}$

Then y = 0 and y = $4\sqrt[n]{a^2b}$

Equation (i) represents a parabola with vertex (0,0) and axis as x–axis,

Equation (ii) represents a parabola with vertex (0,0) and axis as x - axis,

Points of intersection of parabolas are O (0,0) and C($4\sqrt[n]{ab^2}$, $4\sqrt[n]{a^2b}$)

These are shown in the graph below: -

The shaded region is required area, and it is sliced into rectangles of width and length (y1 – y2)ΔX.

This approximation rectangle slides from x = 0 x = 0 to x = $4\sqrt[n]{a^2b}$ so

Required area = Region OQCPO

The area included between the parabolas y2 = 4ax and x2 = 4by is $\frac{16}{3}$ab sq. units