Question 135339This question is from textbook College Algebra
: Thank you for taking the time to help. Here is the target graph equation and the first of a four part question;
Use the graph of y = x^2 -2x -8 to answer the following: a) Using the graph, what are the solution(s) to the equation x^2 - 2x -8 =0?
This question is from textbook College Algebra
Answer by Nate(3500)   (Show Source):
You can put this solution on YOUR website! First, you should always try to factor. Factoring can reduce a lot of work. If the function can not be factored, you would then use the quadratic formula (a quicker way is 'solving the square' if you know how).
ax^2 + bx + c = 0 .. you look for factors of ac that sum to b
1x^2 - 2x - 8 = 0 .. you look for factors of -8 that sum to -2
-8 : -1,8
-8 : -2,4
-8 : -4,2 ... here we are
-8 : -8,1
x^2 - 4x + 2x - 8 = 0 .. mearly break the linear variable's coefficient
(x^2 - 4x) + (2x - 8) = 0 .. group
x(x - 4) + 2(x - 4) = 0 .. factor out
(x + 2)(x - 4) = 0
x + 2 = 0 and x - 4 = 0 .. zero property
x = -2 and x = 4
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