SOLUTION: Please solve the following quadratic equation for x: {{{ x^2-5x-4=0 }}}

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Question 687575: Please solve the following quadratic equation for x: +x%5E2-5x-4=0+
Answer by josh_jordan(263) About Me  (Show Source):
You can put this solution on YOUR website!
To solve this quadratic equation, we can either try factoring, completing the square, or using the quadratic formula. The easiest method is by factoring, so let's see if we can factor this equation.

We need to know if the same 2 numbers that will multiply together and give us -4, can also be added together to give us -5. Let's look at the factors of -4:

-1 x 4 = -4; -1 + 4 = 3

1 x -4 = -4; 1 + -4 = -3

-2 x 2 = -4; -2 + 2 = 0

-4 x 1 = -4; -4 + 1 = -3

4 x -1 = -4; 4 + -1 = 3

None of these work, so, let's try a different method. Let's try the quadratic formula:

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+, a = 1 b = -5 c = -4

=

x+=+%285+%2B-+sqrt%28+25-%28-16%29+%29%29%2F%282%29+ =

x+=+%285+%2B-+sqrt%28+41+%29%29%2F%282%29+, which gives us our final answer:

x+=+%285+%2B+sqrt%28+41+%29%29%2F2, %285+-+sqrt%28+41+%29%29%2F2+