SOLUTION: I need help solving: x(x+2)(x+4)=315 i know the answer, i just have to figure out how to get there other than trial and error.

Question 78021This question is from textbook algebra 1
: I need help solving:
x(x+2)(x+4)=315
i know the answer, i just have to figure out how to get there other than trial and error. This question is from textbook algebra 1

Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!

Foil

Subtract 315 from both sides

Use the calculator's root feature to find one factor. This will allow us to factor the quick way (the other route involves a lot of luck and patience).

So we have one answer of x=5. Lets use the quadratic formula to find the rest:

Solved by pluggable solver: SOLVE quadratic equation with variable

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

The discriminant -131 is less than zero. That means that there are no solutions among real numbers.

If you are a student of advanced school algebra and are aware about imaginary numbers, read on.

In the field of imaginary numbers, the square root of -131 is + or - .

The solution is

Here's your graph:

So our only real answer is x=5

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