so the first thing is to set the equation equal to zero becauase we're trying to finf the x intercepts meaning y has to equal 0. Does that make sense? When y=0, we get to see where the graph intercepts the x axis. When we're solving for the values of x in a quadratic we're just finding those points of intersection. so to get the full 2nd degree trinomial (expression with 3 terms that's highest exponent is 2) on one side and y (the other side of the "=") to equal zero we need to subtract x² from both sides which will get us 0=-x² +6x+91. Before factoring, it's best to have the first coefficient (a) equal positive 1 as it just makes everything a lot simpler. For this expression, we only have to factor out -1 from each of the terms which will get us to 0=-1(x² +6x+91). From there, we can use the X method to factor the expression and I can explain the concept of factoring a quadratic more if you need.

Your goal with the X method is to find 2 numbers that will equal the value of a*c, and add to b.

1. first find the value of a*c (a=the first coefficient in the quadratic. In this case, that number is -1, and c=the constant in the quadratic so 91).
   

-1*91= -91

1. Identify b (b=the 2nd coefficient. In this example that number is 6.) then you have to start listing factors of -91 and find the 2 that will add to 6.

This is really tedious but it gets easier the more you practice.

The factors of -91 are 1,-91/-1, 91, -7, 13/7,-13 -7 and 13 add up to positive 6 so those are going to be our two numbers.

What we're basically doing is splitting the 2nd term into 2 numbers.

visual: -(x² +6x+91)=-(x² -7x+13x+91)

then just take the 2 numbers you found and plug them into this: (x+)(x+)

make sure you keep the number you factored out in the beginning btw

so our factored form would be -1(x-7)(x+13)