The equation of a circle in the first quadrant with centre(a,a) and radius (a)which touches the coordinate axes is:
(x-a)2+(y-a)2=a2...(1)
Differentiating equation(1)with respect to x,we get:
\(2(x-α)+2(y-α)\frac{dy}{dx}=0\)
⇒(x-α)+(y-α)y=0
⇒x-α+yy-αy=0
⇒x+yy-α(1+y)=0
\(⇒α=\frac{x+yy}{1+y}\)
Substituting the value of a in equation(1),we get:
\([x-(\frac{x+yy}{1+y})]^2+[y-(\frac{x+yy}{1+y})]^2=(\frac{x+yy}{1+y})^2\)
\(⇒[(\frac{x-y)y}{(1+y}]^2+[\frac{y-x}{1+y}]^2=[\frac{x+yy}{1+y'}]^2\)
\(⇒(x-y)^2.y^2+(x-y)^2=(x+yy)^2\)
\(⇒(x-y)^2[1+(y)^2]=(x+yy)^2\)
Hence,the required differential equation of the family of circles is
⇒(x-y)^2[1+(y)^2]=(x+yy)^2
Let \( f : \mathbb{R} \to \mathbb{R} \) be a twice differentiable function such that \( f(x + y) = f(x) f(y) \) for all \( x, y \in \mathbb{R} \). If \( f'(0) = 4a \) and \( f \) satisfies \( f''(x) - 3a f'(x) - f(x) = 0 \), where \( a > 0 \), then the area of the region R = {(x, y) | 0 \(\leq\) y \(\leq\) f(ax), 0 \(\leq\) x \(\leq\) 2\ is :