x⁴ - 5x² + 6 is not a quadratic, you say? Correct, it's a quartic (a fourth degree expression). However, it looks rather like a quadratic. In fact, it is quadratic in x², meaning that it is

(x²)² - 5(x²) + 6 = y² - 5y + 6,

where y = x². The quadratic y² - 5y + 6 factors as

y² - 5y + 6 = (y - 3)(y - 2),

so

x⁴ - 5x² + 6 = (x² - 3)(x² - 2).

This is a sometimes useful technique.

Enter this as (x^2 - 3)*(x^2 - 2)

Just close this window to return to the tutorial.
Lost the tutorial to which this window is attached? Press here.