SOLUTION: I need help understanding the method for solving quadratic equations from India. The equation is x^2-2x-13=0. I have tried x^2-2x=13

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Question 251878: I need help understanding the method for solving quadratic equations from India.
The equation is x^2-2x-13=0. I have tried x^2-2x=13
4x^2-8x=52
4x^2-8x+4=52+4
4x^2-8x+4=56
then it asks to take the square root of both sides. Since I cant calculate the square root of 56 I have to believe that I have an error somewhere. Does the negative 2x change my equation?
Thanks for your help.
Found 2 solutions by nyc_function, richwmiller:
Answer by nyc_function(2741) (Show Source):
You can put this solution on YOUR website!
Are you trying to solve x^2 -2x - 13 = 0 for x?
You will need to use the quadratic formula for easy factoring?
Understand?

Answer by richwmiller(17219) (Show Source):
You can put this solution on YOUR website!
Yes the negative 2x changes your equation but it doesn't make it any easier or nicer to solve.
You can't factor this one.
You either need to complete the square or use the quadratic formula
I'll show you complete the square.
And I'll send along the quadratic formula method
Let's start with
x^2-2x=13
so we take the 1/2 of the 2 =1 and square it which still equals 1
add 1 to both sides
x^2-2x+1=14
factor (x-1)^2=14
|x-1|=sqrt(14)
x=1+\-sqrt(14)
----x=1-sqrt(14)= -2.74166---
---x=1+sqrt(14)= 4.74166---
where sqrt(14)=3.74166

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 : .

Discriminant d=56 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 4.74165738677394, -2.74165738677394. Here's your graph: