In order to find the answer to this question, we need to use the quadratic formula.
-b +- √b² - 4ac
2a
In this equation, 5 is a, 16 is b, and -84 is c. You'll notice that the formula says 'plus or minus', meaning that there are two answers depending on whether you add or subtract. Let's start by adding.
-16 + √16² -(4(5)(-84)
2(5)
Use a calculator to simplify. Remember PEMDAS (parentheses, exponents, multiplication and division, addition and subtraction) when deciding which order to go in.
-16 + 44
10
2.8
One solution is 2.8. Now, let's do the same thing, but subtract this time. Keep in mind that the number under the radical stays the same, so you don't have to recalculate that.
-16 - 44
10
-6
The solutions to the equation are 2.8 and -6.
Hope this helps!
