Question 629008
{{{sqrt(2x+21)- sqrt(2x)-3 = 0}}}
{{{sqrt(2x+21) =  sqrt(2x) + 3}}}, square both sides
{{{2x + 21 = 2x + 6sqrt(2x) + 9}}}
{{{6sqrt(2x) = 12}}}
{{{sqrt(2x) = 2}}}, square both sides
{{{2x = 4}}}
{{{x = 2}}}
The x-intercept is 2.
Coordinates: (2,0)
To verify, here's the graph:
{{{ graph( 300, 300, -1, 10, -5, 4, sqrt(2x+21)- sqrt(2x)-3) }}}