Help me solve this please

parc

This is doing my head in, am I missing something really simple?

7a^4 * (3a^4)^2

This some how equals 63a^12

I don't get it. I must be doing the numbers in the parenthesis wrong.

**Timbuk2**

What you have is [latex]\displaystyle{7a^4\times(3a^4)^2}[/latex]
You always do the brackets first so this becomes
[latex]\displaystyle{7a^4\times(9a^8)[/latex]

Remember when multiplying indices, you add the powers, so the above becomes [latex]\displaystyle{63a^{12}}[/latex]

parc

Thanks a lot, but the bit that's confusing me is the part in parentheses

How do you get 9?

Do you square the coefficient of a inside the parentheses by the power ouside it?

so that would be 3^2=9 ?

NoQuarter

Is it 3a^4 MULTIPLYIED by 2 or 3a^4 TO THE POWER OF 2??

Theres a bit of confusion it seems.

apoeiguq3094y

parc wrote: »

Thanks a lot, but the bit that's confusing me is the part in parentheses

How do you get 9?

Do you square the coefficient of a inside the parentheses by the power ouside it?

so that would be 3^2=9 ?

Yeah you square both parts of it.

7a^4 * (3a^4)2
is the same as
7a^4 * (3)^2 * (a^4)2
7a^4 * (3)^2 * (a^4) * (a^4)
7a^4 * 9 * (a^8)

7a^4 * 9a^8
63a^12

**Timbuk2**

Yes, remember the rule of indices [latex](xy)^a = x^ay^a[/latex]

So [latex](3a^4)^2 = (3^2)(a^4)^2[/latex]

Another rule of indices is [latex](x^a)^b = x^{ab}[/latex]

Therefore: [latex](3^2)(a^4)^2 = (3^2)(a^{4\times2}) = 9a^8[/latex]

Does that make sense? Do you understand the rest of it?

apoeiguq3094y

NoQuarter wrote: »

Is it 3a^4 MULTIPLYIED by 2 or 3a^4 TO THE POWER OF 2??

Theres a bit of confusion it seems.

Have to agree with timbuk2, i'd say its to the power of.

**Timbuk2** wrote: »

What you have is [latex]\displaystyle{7a^4\times(3a^4)^2}[/latex]

**Timbuk2**

It's almost definitely to the power of - if it was multiplied by, the convention is to write the 2 before the parentheses. The fact that we got the correct answer by assuming it's to the power of means it should be to the power of, and it's just a typo in the original post.

parc

NoQuarter wrote: »

Is it 3a^4 MULTIPLYIED by 2 or 3a^4 TO THE POWER OF 2??

Theres a bit of confusion it seems.

Yeah sorry, to the power of 2. Just changed my original post

parc

**Timbuk2** wrote: »

Yes, remember the rule of indices [latex](xy)^a = x^ay^a[/latex]

So [latex](3a^4)^2 = (3^2)(a^4)^2[/latex]

Another rule of indices is [latex](x^a)^b = x^{ab}[/latex]

Therefore: [latex](3^2)(a^4)^2 = (3^2)(a^{4\times2}) = 9a^8[/latex]

Does that make sense? Do you understand the rest of it?

Got it thanks