Question 403486
This easy.

Check what a^2 + b^2 equals 

And then what C^2 equals 

A being the short side ( 3 ) and B being the medium one ( 4) And C being the longest ( 5 ) 

So (3)^2 + (4)^2 = 25 

And (5)^2 = 25 

If the longest side squared equals the sum of the legs squared >>  the triangle is a right triangle.

If the longest side squared is less than the sum of the legs squared >> the triangle is acute.

If the longest side squared is greater than the sum of the legs squared >> the triange is obtuse.

So yours is a right triangle.