Biquadratic equations

A biquadratic equation is a 4-degree equation without the terms of degree 1 and 3.

To solve a biquadratic equation you have to do a change of variable: z = x². Then you have to solve the quadratic equation and finally undo the change.

Example 1:

Example 2:

 

Exercise: Solve the following equations:

a) x⁴ -13x² +36 = 0

b) x⁴ +7x² +13 = 0

 

 

Solutions: a)±2,±3;  b) Φ