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Mathematics 5 Online
OpenStudy (anonymous):

pleae factorise step by step

OpenStudy (anonymous):

\[x ^{4}-(x-z)^{4}\]

OpenStudy (mertsj):

\[[x^2-(x-z)^2][x^2+(x-z)^2]\]

OpenStudy (anonymous):

ya

OpenStudy (anonymous):

k

OpenStudy (anonymous):

can somone help me?!!!!!

OpenStudy (mertsj):

\[[x-(x-z)][x+[x-z)][x^2+(x-z)^2]\]

OpenStudy (anonymous):

the answer is \[z(2x-z)(2x ^{2}-2xz+z ^{2})\]

OpenStudy (bahrom7893):

ima get confused if i type, so I'll just write it out on paper.. hold on

OpenStudy (anonymous):

plzz do it step by step

OpenStudy (bahrom7893):

So we're here right? (x^2-(x-z)^2)(x^2+(x-z)^2)

OpenStudy (bahrom7893):

that's by using a^2-b^2 = (a-b)(a+b)

OpenStudy (anonymous):

k

OpenStudy (bahrom7893):

where a = x^4, b = (x-z)^4

OpenStudy (bahrom7893):

Right, so now expand the insides.

OpenStudy (anonymous):

\[(x^2-(x-z)^2)(x^2+(x-z)^2)\]

OpenStudy (bahrom7893):

(x^2-(x-z)^2)(x^2+(x-z)^2) = (x^2 - [x^2-2xz+z^2])(x^2 + [x^2-2xz+z^2])

OpenStudy (anonymous):

\[(x^2-(x-z)^2)(x^2+(x-z)^2) = (x^2 - [x^2-2xz+z^2])(x^2 + [x^2-2xz+z^2])\]

OpenStudy (bahrom7893):

(x^2 - [x^2-2xz+z^2])(x^2 + [x^2-2xz+z^2]) = (x^2-x^2+2xz-z^2)(x^2+x^2-2xz+z^2)

OpenStudy (bahrom7893):

= (2xz-z^2)(2x^2-2xz+z^2)

OpenStudy (bahrom7893):

now pull out a z from the first parenthesis: z(2x-z)(2x^2-2xz+z^2)

OpenStudy (anonymous):

k

OpenStudy (anonymous):

\[ x ^{4}-(x-z)^{4} = (x^2 +(x-z)^2) \times (x^2 - (x-z)^2)\] using, \( a^2-b^2= (a+b)(a-b) \) Applying the same thing on \( (x^2 - (x-z)^2) \) we will get \( (x - (x-z))\times (x + (x-z)) = z(2x-z) \) now, \(x^2 +(x-z)^2 = 2 x^2-2 x z+z^2 \) Now we have to put together the pieces we get \( x ^{4}-(x-z)^{4} = (2 x-z) z \left(2 x^2-2 x z+z^2\right) \)

OpenStudy (anonymous):

Mertsj, I am not sure why I am wrong, but apparently wolfram is making a same mistake ( http://www.wolframalpha.com/input/?i=Factor%5Bx%5E4+-+%28x+-+z%29%5E4%5D ) Or am I missing something real silly? :)

OpenStudy (mertsj):

|dw:1329144181053:dw|

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