Question 703831
A triangle is obtuse if {{{k^2 > a^2 + b^2}}} - in other words if the square of the longest side is larger than the sum of the squares of the smaller two sides.<P>
In this case {{{k^2 > 81+169}}} ---> {{{k^2 > 250}}} --->  {{{k > 15.811...}}}
There are an infinite number of solutions to that equation.

<P>Hope the solution helped.  Sometimes you need more than a solution.  Contact fcabanski@hotmail.com for online, private tutoring, or personalized problem solving (quick for groups of problems.)