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# Help with this algebra and functions question please?

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1. I got to part (b) and now I'm stuck. I have a+b = 7 and -8a+4b = 4 and now I don't know how to go about getting the value of a and b
2. (Original post by jessnoch)

I got to part (b) and now I'm stuck. I have a+b = 7 and -8a+4b = 4 and now I don't know how to go about getting the value of a and b
You have two equations. Two unknown values. How do you reduce it to one unknown value?
3. (Original post by High Stakes)
You have two equations. Two unknown values. How do you reduce it to one unknown value?
I don't know, I think I'm being dumb
4. (Original post by jessnoch)
I don't know, I think I'm being dumb
If a + b = 7, then a = 7 - b right?

How can I use that information in the other equation?
5. To get the value of a and b, you have to solve the two equations simultaneously.

The two equations we have are:

a + b = 7 and -8a + 4b = 4.

Rearrange the first equation to make a the subject.
a = 7 - b

Subsitute the rearranged equation into the second equation of -8a + 4b =4.

-8(7 - b) + 4b = 4

Simplify This subsitution to solve for b by expanding the brackets:

-8(7 - b) + 4b = 4 = -56 + 8b + 4b = 4

Now solve for b( collecting like terms)
(move the -56 to the other side to get +56 so that makes 12b = 60
12b = 60
b = 5

Subsituteb = 5into any of the equations to find the value of a:

a = 7 - (5)
a = 2

So you values for a and b are:

a = 2 and b = 5.
6. (Original post by crystala1998)
...
Please don't post full solutions - it's against the rules of this forum.

The first half of your post would have been great to allow the OP to finish it themselves.

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