# Talk

(11 Posts)
SpartacusWoman Thu 19-Jan-17 17:57:24

DDs been doing her homework, it's a printout sheet from mathsbox.org and looks like some sort of skills check, she is stuck on two questions.

Expand and simplify 3(a+3b)+2(a+b)

Expand and simplify 5(4a-3b)+4(2a-2b)

She hasn't done any expanding or simplifying at school yet and i suggested she leave them blank and I'll pop note in explaining but she is anxious she will get detention and is stressing herself. She hasn't asked me for help because she knows I struggle with anything more than knowing what's in my purse and how much change I need for a tenner and didn't want me to feel stupid.

She had similar before and after some lovely MNers helped me, but the questions were seperate drew into ones to expand and ones to simplify, but these sums are quite a bit longer and I'm out of my depth again. I don't know which part of the sum to expand, and which part to simplify.

I think we could expand the whole sum, or simplify the whole sum
So second one simplified would be
9(6a-5b) ?

but not sure how to do both on one sum?

Thank you for any help you can give, I feel really thick with this .

NCforQuestion Thu 19-Jan-17 18:03:30

Multiply out the brackets the outline terms together.

E.g. 3(a + 3b) become 3a + 9b

NCforQuestion Thu 19-Jan-17 18:03:47

*put like terms

NCforQuestion Thu 19-Jan-17 18:04:53

On iPad so struggling to type but can jump on pc if you need me to.

EllenJanethickerknickers Thu 19-Jan-17 18:11:22

As NC says, multiply the elements inside the brackets by the number immediately before, then group like terms together. 2(a+b) = 2 times a + 2 times b = 2a + 2b
3(a +3b) = 3a+ 9b
bidmas, you have multiplied first.

Then group, 2a + 3a +2b + 9b=
5a+ 11b

Also, remember to check whether the number is positive or negative, so 5(4a - 3b) becomes 20a - 15b.

SpartacusWoman Thu 19-Jan-17 19:02:26

I showed my Daughter the posts and she's currently having a go. I've had a pop and come up with

28a-23b

Is that correct or should i have another look?

Thank you so much again for all the help.

Gruffalosgrandma Thu 19-Jan-17 19:10:42

3(a+3b) + 2(a+b)
= 3a + 9b + 2a + 2b
= 3a + 2a + 9b + 2b
= 5a + 11b

If that makes sense the second one is done exactly the same way and you should indeed get 28a - 23b

MuseumGardens Thu 19-Jan-17 20:44:20

Hooray for the kind mnetters.

maz99 Thu 19-Jan-17 22:46:27

Have a look at the website mathsisfun.com - it explains things very clearly

kimlek Fri 20-Jan-17 11:58:55

Khan academy is also really good at explaining stuff!
I'd still put a note on her bookto highlight to the teacher that she needs this explaining.

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