# Math Help - more factoring

1. ## more factoring

more factoring...

a) 21 $x^5$ $y^4$ $z^6$-15 $x^4$ $y^2$ $z^8$+36 $x^8$ $y^3$ z
b) $x^3$-5x+4
c)4 $x^4$-8 $x^3$-20 $x^2$-48x
d) $x^4$+ $x^3$-4 $x^2$+5x-3

Thank you

2. I've made some progress...not really, actually

for a) i got 3 $x^4$ $y^2$z (7x $y^2$ $z^5$-5 $z^7$+12 $x^4$y)......I'm not sure if this is the last step or if there's more...

3. Hello, johett!

The first one has a common factor . . . and that's all.

The others require knowledge of the Factor Theorem.

$a)\;21x^5y^4z^6 -15x^4y^2z^8+36x^8y^3z$
$3x^4y^2z\left(7xy^2z^5 - 5z^7 + 12x^4y\right)$ . . . You got it! . . .Good!

$b) \;x^3 - 5x+4$
$(x-1)(x^2+x-4)$

$c)\;4x^4 -8x^3-20x^2-48x$
$4x(x-4)(x^2+2x+3)$

$d) \;x^4+x^3-4x^2+5x-3$
$(x-1)(x+3)(x^2-x+1)$