Posted by **jerroyle** on Friday, August 23, 2013 at 9:28am.

what is the factor of a^4-7a^2+9 ?

- math -
**Steve**, Friday, August 23, 2013 at 12:39pm
a^4-7a^2+9

a^2 = (7±√13)/2

Now it gets tricky:

7+√13 = (1+2√13+13)/2 = (1+√13)^2/2

So, if

a^2 = (7+√13)/2 = (1+√13)^2/4

a = ±1/2 (√13+1)

and

a = ±1/2 (√13-1)

Makes things kind of nasty, the factors are

1/16 (±2x + √13 ± 1)

where all 4 combinations of + and - are used.

- math -
**MathMate**, Friday, August 23, 2013 at 12:40pm
Hint:

substitute u=a^2, then

a^4-7a^2+9

=u^2-7u+9

and try to factorize.

However, check you question to see if there is a typo. The above expression in u does not have rational factors.

## Answer This Question

## Related Questions

- math - If the sides of a box all double in length, by how much does its volume ...
- Math - Use the Factor Theorem to determine whether x-3 is a factor of P(x)=2x^3-...
- science help - Two factors which cause global climate change are listed below. ...
- stats - two factor ANOVA indep measures exper. 2 level factor A 3 level factor B...
- itc c++ - can any one please dry run this code #include<iostream> using ...
- math - Is 3 a factor of 261? Is 10 a factor of 325? Is 6 a factor of 492?
- math 1350 - Find the three digit number that satisfies the following conditions...
- MATH 101 - Factor completely. Be sure to factor out the greatest common factor ...
- Factor - How do I factor these: 2x2 - 16x + 30 4x^2-9 x^2-5x 5x^2-26x+5 25x^2+4 ...
- Math - Factor Completely: I am really confused on how to start it. 12q^5w^2-36q^...

More Related Questions