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# Algebra and functions C2 exam question help watch

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. ah this is simultaneous equations from c1. firstly you must make one term from each equation the same (id recommend multiplying all of a+b=7 by 4, but you can do this slightly differently by x -8 and eliminating a).
this leaves you with -8a+4b=4 and 4a+4b=28
because the both 4b's are positive, you subtract the second equation from the first.
-8a - 4a= -12a
4b-4b=0 (eliminating the term)
4-28=-24
now we have -12a=-24, solving gives a=2.
now substitute a=2 into ur a+b=7 to get 2+b=7
b=5 (therefore a=2,b=5)
3. (Original post by Toasticide)
ah this is simultaneous equations from c1. firstly you must make one term from each equation the same (id recommend multiplying all of a+b=7 by 4, but you can do this slightly differently by x -8 and eliminating a).
this leaves you with -8a+4b=4 and 4a+4b=28
because the both 4b's are positive, you subtract the second equation from the first.
-8a - 4a= -12a
4b-4b=0 (eliminating the term)
4-28=-24
now we have -12a=-24, solving gives a=2.
now substitute a=2 into ur a+b=7 to get 2+b=7
b=5 (therefore a=2,b=5)
Thankyou so much!! I don't know why I didn't think of simultaneous equations, dumb moment obviously

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Updated: April 24, 2016
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