X^2-4=5X Solve for X?

Question

(x+2)(x-2)=5x
x+2=5x or x-2=5x
2=4x or -2=4x
x=2/4 or x=-2/4
what did i do wrong?...

Answer 1

Should have been like this: x^2-5x-4=0
So, by the quadratic equation, [5+-sqrt(25+20)]/2.

Answer 2

X^2 - 4 = 5x
X^2 -5x -4 = 0 This is a quadratic equation.
The Quadratic Formula. The quadratic equation
has the solutions frrom the general form:

ax^2 + bx + c = 0
x = [-b (+or-) (b^2 - 4ac)^(1/2)] / 2a
For your problem
a=1
-b = 5
c = - 4

Search the web for "Qudratic Equations" to get a more readable form of the solution. . Plug in the numbers and get the solution

x = [5 +or- (25 -16)^1/2]/2
x = [5 +or- 9^1/2]/2
x = (5 + 3)/2 = 4 , and
x = (5 - 3)/2 = 1

Substitute these values into the equation to check for correctness.

Answer 3

Here's where you went wrong:
From (x+2)(x-2) = 5x <--- That's fine.
But it doesn't mean that:
x+2 = 5x or x-2 =5x
Just sorta doesn't work like that. It would work if the right hand side of the equation is zero, but it isn't.
You're basically looking at this situation:
x^2 - 5x - 4 = 0
Doesn't look like it's going to be really pretty to factor, so we'll just complete the square:
x^2 - 5x = 4
x^2 - 5x + 25/4 = 4+25/4
x^2 - 5x + 25/4 = 41/4
(x-5/2)^2 = 41/4
x = 5/2 +- sqrt(41/4)

Edit: Psst: James: c = 4, so 4ac = 16, not 20 :-)

Answer 4

ok the answer is square root of 41 plus 5 and all divided by 2. I cannot seem to be able to paste the equation. but it could also be read as X= ((41^1/2)+5)/2

Answer 5

x+2=5x
2=4x
x=2/4=1/2

x-2=5x
-2=4x
x=-2/4=/1/2

i believe you just didn't simplify.

Answer 6

Sure it's x^2-4? I can solve it if it's x^2+4, but I'm not sure of any other way to do it as it is besides how you did it.

Answer 7

x = 2/4 = 1/2
x = -2/4 = -1/2

Answer 8

Are you guys joking, how can x = 1/2?

Answer 9

Your are true.