Question

please help I don't know how to do this

Factor this expression completely.

x2 - r2

I will medal

Answer 1

(x+r)(x-r)

Answer 2

can you explain this to me?

Answer 3

no

Answer 4

okay then..

Answer 5

2

Answer 6

to factor something you need to break it up into components that multiply togjether to make the original.

so you can see that x^2 must break into x * x

Answer 7

oh okay that makes sense thank you

Answer 8

so the factors must be
(x+a)(x+b)

if you multiply that out you will get
x^2 +ax +bx + b^2

if you compare that with the original you can see that there are NO terms with x in them

therefore a=-b (so that they cancel out)

if you compare with te original again you can see that the b^2 term equates to r^2

therefore b = r

so we know b= r and a=-b so a= -r

so the factors are (x+r)(x-r)

Answer 9

@MrNood
Factor this expression completely.

2x^2 + 11^x + 15

(2*x+x)+(11*x+15)?

Answer 10

you can check that by expanding again:

(x+r)(x-r) = x^2 +rx -rx -r^2

Answer 11

so we are looking for factors tha tproduce a term with 2x^2

this can ONLY be 2x * x

so our factors are (2x+a)(x+b)

try to expand that pair and see what you get....

I'll help if oyu do that...

Answer 12

expand (2x+a)(x+b)?

Answer 13

yes - multiply them out completely

Answer 14

2xa*xb?

Answer 15

or 2x^2ab

Answer 16

no

use 'FOIL' method? you must multiply both terms in each bracket by both in the other

Answer 17

idk what FOIL method is or I can't recall it

Answer 18

2x^2ab*2x^2ab? is it that?

Answer 19

??? @MrNood

Answer 20

FOIL is 'First, Outer, Inner, Last'

Multiply first pair in each bracket
then outer pair
then inner pair
then last pair