Answer:a. [tex]2\sqrt{31}[/tex] b. 3c. [tex]3\sqrt{5}[/tex]d. [tex]2\sqrt{3}[/tex]Step-by-step explanation:This is a simple quadratic formula "substitution".Essentially what you do is replace the "b" in the formula given above, with a "b" value from your given choices, same goes for "a" and "c" values. You replace them and then solve the quadratic formula equation. Ex. For the first set of values in your question, you make the formula into: [tex]\sqrt{2^2-4(5)(-6)[/tex] And there you would solve normally.2 squared is 4, so you get 4 - [4 * 5 * -6]Which after solving leaves you with: [tex]\sqrt{2^2+124}[/tex]Then you do Prime Factorization of 124, leaving you with: [tex]\sqrt{2^2*31}[/tex]Then you apply the radical rule, leaving you with: [tex]2\sqrt{31}[/tex]