Respuesta :
When you have a quadratic equation in this form, i.e. with the x^2 coefficient set to one, you can find its solution with a little shortcut.
Instead of using the quadratic formula, you can find the solutions like this: if you read the equation as
[tex] x^2-sx+p [/tex]
then [tex] s [/tex] is the sum of the solutions, and [tex] p [/tex] is their product.
Since [tex] s[/tex] has a minus sign in front of it, the sum of the solutions must be -3. Also, their product has to be -18.
Since the product is negative, the two numbers have opposite sign. Since the sum is also negative, the biggest number (in absolute value) is the negative one.
You can have 18 as a product by choosing 1 and -18, 2 and -9 or 3 and -6.
This last couple sum to -3, so the two solutions are 3 and -6
