1. ## 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

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

Thanks

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

2. $\displaystyle (x+1)\cdot(x^2+3x+5) = x\cdot x^2 + x\cdot 3x + x\cdot 5 + 1\cdot x^2 + 1\cdot 3x + 1\cdot 5 = x^3 + 4x^2 + 8x + 5$

3. Thanks, but im really still not sure what to do.. any more hints?

4. Hi fvaras89

Can you expand (x+5)^2 ?

5. Is that how you would expand it?

x^2 + 25x + 25

6. Hi fvaras89

Almost right. How can you get 25x ?

7. oh woops hahah..

so would it be x^2 + 25?

8. Hi fvaras89

Still no.

$\displaystyle (x+a) \cdot (y+b) = x \cdot y + x \cdot b + a \cdot y + a \cdot b$

9. 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:

$\displaystyle (x+5)^2$

since the power is 2 it's multiplying itself.

for example $\displaystyle 2^2$

= $\displaystyle 2 * 2$

now we do the same for this..

$\displaystyle (x+5)(x+5)$

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

$\displaystyle x * x = x^2$

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

$\displaystyle x * 5 = 5x$

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

$\displaystyle 5 * x = 5x$

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.

$\displaystyle 5 * 5 = 25$

do you get the pattern?

Now put them together

$\displaystyle x^2 + 5x + 5x + 25$

simplify..

$\displaystyle x^2 + 10x + 25$

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:

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

$\displaystyle (x+5)^2$

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

now just substitute:

$\displaystyle a^2 + 2ab + b^2$

$\displaystyle x^2 + 2*x*5 + 5^2$

$\displaystyle x^2 + 10x + 25$

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

Do you understand better now?

10. ## help

i dont understand 6(x+4)
7(3x-9)
x(x+7)
as soon as thanks

11. WHAT are you asked to do?

12. 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 so please could you help
thanks Natalie B

13. 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

1.

2.

15. 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 ???

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