Question

factor (x² - 9)

Answer 1

do you know formula a^2 -b^2 =?

Answer 2

no

Answer 3

@ateryu This is called the difference of squares. In general, \((a^2-b^2)=(a+b)(a-b)\). Can you apply that to your question to get the answer?

Answer 4

i dunno how to factorise it.. can u teach me?

Answer 5

prove from x*x-3*3

Answer 6

The first step is to figure out how it fits the difference of squares formula. You need to figure out what the \(a\) and the \(b\) are in your problem to fit into \((a^2-b^2)\). Here is a hint, your problem can be rewritten as \((x^2-3^2)\)

Answer 7

u mean like this (a-b) (a-b)
a*a=a² b*b=b²
a*b=ab b*a=ab
then a²-ab-ab-b²
like that?

Answer 8

minus time minus = ?

Answer 9

oh..sorry..minus time minus is plus right?

Answer 10

yes then ?

Answer 11

and -ab-ab =?

Answer 12

the answer should be a²+ab-ab-b²

Answer 13

Not (a-b)(a-b), it's (a+b)(a-b). If you multiply that you get \(a^2+ab-ab-b^2\), which simplifies to \(a^2-b^2\)

Answer 14

-ab-ab is zero? or need to plus?

Answer 15

oh..i see...thanks...now i understand...thank you very much@nbouscal