SOLUTION: how do you factor x^4 - X^2 - 20. I got (x^2+4)(x^2-5) but it is supposedly the wrong answer. Also tried x^2(x+1)(x-1)-20. still wrong.

Question 883719: how do you factor x^4 - X^2 - 20. I got (x^2+4)(x^2-5) but it is supposedly the wrong answer. Also tried x^2(x+1)(x-1)-20. still wrong.
Answer by josgarithmetic(39617) (Show Source): You can put this solution on YOUR website!
X is a misprint.
Starting from try conveniently substituting like and rewrite the expression as . You can take your guesses using 5 and 4 and hopefully find , and this obviously works ----- the expression using u.

Now substitute back for u:
.
The answer key is wrong.
YOUR first result was correct.
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