How do you rationalize the denominator and simplify h / (sqrtx - sqrt( x+h))hxx+h?

1 Answer
Apr 24, 2016

h/(sqrt(x)-sqrt(x+h))=-(sqrt(x)+sqrt(x+h))hxx+h=(x+x+h)

Explanation:

The difference of squares identity can be written:

a^2-b^2=(a-b)(a+b)a2b2=(ab)(a+b)

We use this with a=sqrt(x)a=x and b=sqrt(x+h)b=x+h later.

color(white)()
Multiply numerator and denominator by (sqrt(x)+sqrt(x+h))(x+x+h):

h/(sqrt(x)-sqrt(x+h))hxx+h

=(h(sqrt(x)+sqrt(x+h)))/((sqrt(x)-sqrt(x+h))(sqrt(x)+sqrt(x+h))=h(x+x+h)(xx+h)(x+x+h)

=(h(sqrt(x)+sqrt(x+h)))/((sqrt(x))^2-(sqrt(x+h))^2)=h(x+x+h)(x)2(x+h)2

=(h(sqrt(x)+sqrt(x+h)))/(x-(x+h))=h(x+x+h)x(x+h)

=(color(red)(cancel(color(black)(h)))(sqrt(x)+sqrt(x+h)))/(-color(red)(cancel(color(black)(h))))

=-(sqrt(x)+sqrt(x+h))