If these sides formed a right triangle, then a^2 + b^2 = c^2 would be true
a & b are the two legs
c is the hypotenuse (longest side)
a = 4.5
b = 6
c = 7.5
Plug those values into the pythaogrean theorem and let's see if we get a true equation or not
a^2 + b^2 = c^2
4.5^2 + 6^2 = 7.5^2
20.25 + 36 = 56.25
56.25 = 56.25 .... true equation
Since we get a true equation, this means the original equation is true for the given a,b,c values. So we do have a right triangle.