Question

Quadratic equations:
Solve for x:
X4 - 5X2 + 4 = 0

Answer 1

In quadratic form, the equation would be -5x2 + x4 + 4 = 0

Answer 2

Wouldn´t this equation written in this way x^4-5x^2+4=0

Answer 3

?

Answer 4

But you would have to have the equation in ax^2 + bx + c form

Answer 5

If this equation has the form above so try to factor out.

Answer 6

-5x2 + x4 + 4 = 0. From here you can use (x^2-4)(x^2-1);

Answer 7

Reminder if ab=0 then a=0 or b=0

Answer 8

X^4-5X^2+4=0

Substitute u=X^2 into the equation. This will make the quadratic formula easy to use.
u^2-5u+4=0
u=X^2

Move -4 to the left-hand side of the equation by adding it to both sides. The goal is to have all terms on the left-hand side equal to 0.
u^2-5u+4=0

In this problem -1*-4=4 and -1-4=-5, so insert -1 as the right hand term of one factor and -4 as the right-hand term of the other factor.
(u-1)(u-4)=0

Set each of the factors of the left-hand side of the equation equal to 0.
u-1=0
u-4=0

Since -1 does not contain the variable to solve for, move it to the right-hand side of the equation by adding 1 to both sides.
u=1
u-4=0

Set each of the factors of the left-hand side of the equation equal to 0.
u=1
u-4=0

Since -4 does not contain the variable to solve for, move it to the right-hand side of the equation by adding 4 to both sides.
u=1
u=4

The complete solution is the set of the individual solutions.
u=1, 4

Substitute the real value of u=X^2 back into the solved equation.
X^2=1
X^2=4

Solve the first equation for X.
X^2=1

Take the square root of both sides of the equation to eliminate the exponent on the left-hand side.
X=+/-sqrt(1)

Pull all perfect square roots out from under the radical. In this case, remove the 1 because it is a perfect square.
X=+/-1

First, substitute in the + portion of the +/- to find the first solution.
X=1

Next, substitute in the - portion of the +/- to find the second solution.
X=-1

The complete solution is the result of both the + and - portions of the solution.
X=1,-1

Solve the second equation for X.
X^2=4

Take the square root of both sides of the equation to eliminate the exponent on the left-hand side.
X=+/-sqrt(4)

Pull all perfect squXre roots out from under the radical. In this case, remove the 2 because it is a perfect square.
X=+/-2

First, substitute in the + portion of the +/- to find the first solution.
X=2

Next, substitute in the - portion of the +/- to find the second solution.
X=-2

The complete solution is the result of both the + and - portions of the solution.
X=2,-2

The solution to X^4-5X^2+4=0 is X=1,-1,2,-2.
X=1,-1,2,-2

Answer 9

Two different ways of solving but the same answer.