Mathermatical Genius?????????

[poopy]

Solve the equation & if poss explain how you got to your answer, so i can understand:

8 (b+4) = 5(b-8)

[gen2]

Expand the brackets then gather like terms together.

[sohcahtoa]

The 8 in front of the brackets means both b and 4 are to be multiplied by 8 --- giving 8b + 32 Similarly for 5(b-8) -- giving 5b - 40
So now you have 8b+32 = 5b - 40
Then take 5b from each side - giving 3b + 32 = -40
Then take 32 from each side giving 3b = -72
Then divide each side by 3 giving b = -42.

[Christiana]

I'm not a mathematical genius so this might be wrong but here goes.
First it means 8 x (b + 4) etc. so to get rid of the brackets mulitipy which gives you 8b + 32 and on the other side of the equals sign 5b - 40
You now have 8b + 32 = 5b - 40. Now gather all the 'b's on one side and numbers on the other. Crossing the equals sign changes the plus or minus to the opposite, so you end up with 8b - 5b = - 32 - 40. That is 3b = - 72 ( Notice you have two lots of minusses which together come to 72). So divinding by 3 just b = -24.

[Uzoma]

If you expand the brackets it equates to 8b + 32 = 5b - 40. When you take the unknowns (the ones with 'b' in them to one side of the = sign and the ones without a 'b' to the other side they change from positive to negative or vice versa. This means that 8b + 32 = 5b - 40 is the same as 8b - 5b = - 40 - 32. This means that 3b = - 72. b = -24. I hope that this makes sense.

[Christiana]

I think sohcahtoa got her 2 and 4 round the wrong way. You can test your answer by substitution. That is go back to the original sum and insert -24 for the b's. You get 8 x ( -24+4) = 5 x (-24 - 8), thus 8 x - 20 = 5 x - 32 (Notice again you need to add the two minuses in the brackets) Hope that helps.

[sohcahtoa]

Yes - I meant to write -24 at the end. Sorry

[poopy]

Thank you all. i am most impressed