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# rearrange equation Watch

1. hi all
please can anyone help with this equation stuck tight with it

need to make b the subject of this equation

7a= b/5 -3c (bc+2).

Eggie
2. (Original post by eggie)
hi all
please can anyone help with this equation stuck tight with it

need to make b the subject of this equation

7a= b/5 -3c (bc+2).

Eggie

Can you do it from there?
3. (Original post by RDKGames)

Can you do it from there?
Hi RDk

The question i have is this that a student makes a mistake in attempting the equation as follows
7a= b/5 -3(bc+2)

he writes it as this

7a= b/5 - 3 (bc+2)
35a = b-3 (bc-2)
35a = b-3bc + 6
35a - 6 = b(1-3c)

b = 35a - 6 / 1-3c

so somewhere he is wrong i cant figure the equation out so i cant find the mistake that he made. 2 mistakes are made in the attempt of the equation.

so any help appreciated.

eggie
4. (Original post by eggie)
Hi RDk

The question i have is this that a student makes a mistake in attempting the equation as follows
7a= b/5 -3(bc+2)

he writes it as this

7a= b/5 - 3 (bc+2)
35a = b-3 (bc-2)
35a = b-3bc + 6
35a - 6 = b(1-3c)

b = 35a - 6 / 1-3c

so somewhere he is wrong i cant figure the equation out so i cant find the mistake that he made. 2 mistakes are made in the attempt of the equation.

so any help appreciated.

eggie
Okay you wrote it out slightly differently from the first time.

Assuming the equation is:

Second line when he is multiplying through by 5. The last term should go to -15(bc+2). Also the sign of 2 in the bracket changes in this line, not supposed to happen. Everything else looks fine.

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