# Expanding expressions

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• Aug 16th 2009, 11:41 PM
fvaras89
Expanding expressions
Im not too sure how to expand these two expressions

1/ (x+2y)(x-2y)2

2/ (1-x)(1+x+x2+x3)

The small numbers r squared and cubed.. not sure how to use it here (Worried)

Would be good if you can put steps also so i can understand where it comes from..(Happy)

Thanks
• Aug 17th 2009, 12:01 AM
songoku
Hi fvaras89

Example
To type square : x^2
To type cube : x^3

or you can learn it here : http://www.mathhelpforum.com/math-he...-tutorial.html

1. $(x+1)^2 = (x+1) * (x+1) = x^2 + x + x + 1 = x^2 + 2x + 1$

2. $(x+1)\cdot(x^2+3x+5) = x\cdot x^2 + x\cdot 3x + x\cdot 5 + 1\cdot x^2 + 1\cdot 3x + 1\cdot 5 = x^3 + 4x^2 + 8x + 5$
• Aug 17th 2009, 12:08 AM
fvaras89
Thanks, but im really still not sure what to do.. any more hints? (Crying)
• Aug 17th 2009, 12:20 AM
songoku
Hi fvaras89

Can you expand (x+5)^2 ? :)
• Aug 17th 2009, 12:59 AM
fvaras89
Is that how you would expand it?

x^2 + 25x + 25
• Aug 17th 2009, 01:02 AM
songoku
Hi fvaras89

Almost right. How can you get 25x ? :)
• Aug 17th 2009, 01:04 AM
fvaras89
oh woops hahah..

so would it be x^2 + 25?
• Aug 17th 2009, 01:17 AM
songoku
Hi fvaras89

Still no. :)

$(x+a) \cdot (y+b) = x \cdot y + x \cdot b + a \cdot y + a \cdot b$
• Aug 18th 2009, 12:10 AM
jgv115
Do you have a text book that you are working from? I doubt your teacher would give you a task if you're not clear.

I'll use songoku's question:

$(x+5)^2$

since the power is 2 it's multiplying itself.

for example $2^2$

= $2 * 2$

now we do the same for this..

$(x+5)(x+5)$

now we multiply the first number/letter of the first bracket by the first number/letter of the second bracket

$x * x = x^2$

now we multiply the first letter of the first bracket by the second number/ letter

$x * 5 = 5x$

now we multiply the second letter/number by the first number of the second bracket

$5 * x = 5x$

now the last step... yep that's right, the second number/letter of the first bracket by the second number/letter of the second bracket.

$5 * 5 = 25$

do you get the pattern?

Now put them together

$x^2 + 5x + 5x + 25$

simplify..

$x^2 + 10x + 25$

now that you've learnt how to do it properly now I tell you the shortcut

when you have 2 brackets multiplying each other and they are IDENTICAL. They have to be identical.

The formula:

$a^2 + 2ab + b^2$ can be used.. for example:

$(x+5)^2$

x will be "a" and 5 will be "b"

now just substitute:

$a^2 + 2ab + b^2$

$x^2 + 2*x*5 + 5^2$

$x^2 + 10x + 25$

Was that the same answer as before? it sure was.

Do you understand better now?
• May 5th 2010, 08:37 AM
NatalieB
help
i dont understand 6(x+4)
7(3x-9)
x(x+7)
as soon as thanks
• May 5th 2010, 10:30 AM
Wilmer
WHAT are you asked to do?
• May 5th 2010, 10:39 AM
NatalieB
Sorry i am new to this...
i am asked to expand these alebraic expressions
5(x+5)
9(8x-9)
x(x+8)
and i really dont understand them (Wondering) so please could you help
thanks Natalie B (Rofl)
• May 5th 2010, 12:31 PM
Wilmer
Quote:

Originally Posted by NatalieB
i am asked to expand these alebraic expressions
5(x+5)
9(8x-9)
x(x+8)

Means multiply what's inside brackets by what's outside.
Take 5(x+5)
5 times x = 5x
5 times 5 = 25
So answer is 5x + 25

Let's see you do the other 2: GO Natalie GO (Rock)
• May 5th 2010, 10:11 PM
coolnice
• May 6th 2010, 08:10 AM
NatalieB
Okayy so is this correct ...?
9(8x-9)
9 times 8x=72x
9 times 9 = 81
so its 72x-81

P.S
how do you add the quote in at the top of the page ??? (Rofl)(Thinking)
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