Algebra ...

[Shekii]

Guys I need help.

Could you tell me a good method so I can work out bracketed equations because I've tried and tried and failed. If you could help this would get on top of maths.

7(x-1)=21

 

[HK]

Okay, I'm not exactly a math genius, but I think X = 4 in this case.

My logic is as follows. 7 goes into 21 three times, so the equation should be 7 x 3 = 21. Since (x-1) must be the 3 part, it's then easy to see x must be 4.

That's probably horribly wrong, but it felt good.

 

[HK]

I'm really not sure of a method you could use for this. For me, it's just 'look at the equation and determine what makes sense'.

 

[Shekii]

Actually your right, but I don't really get your method. That was an example off the internet which I don't understand lol.

 

[Hekler]

...it's been too long for me to remember. I usually will just down a few of these and make a guess.

 

[Kyle B]

Guys I need help.

Could you tell me a good method so I can work out bracketed equations because I've tried and tried and failed. If you could help this would get on top of maths.

7(x-1)=21

First multiply.

7(x-1)=21
becomes:
7x-7=21
add 7
7x=28
divide by 7
x=4

Edit: Basically, if you have parenthesis like that, multiply it out to eliminate them.

 

[Shekii]

Ahh brilliant Kyle thanks very much, now I'm practise it over and over again

 

[HK]

Okay. I guess you need to look at the parts of the equation that make sense, and determine the relationship between them.

In this case, you have the number 7 and 21. You know that 21 will be the sum of the equation, the total. So now you just need to know what number, when multiplied by seven, will lead you to 21. That's easy - 7 times 3 is 21. So you know that the number in the brackets has to be 3, and from there it's easy to see that x must be 4.

Iam confused though - there's no symbol between the 7 and the brackets in that equation. Should there be one? It's been a while since I did algebra, I can't remember if you assume it's a multiplication when it looks like that.

It's just working backwards from the total.

 

[Abcinthia]

Okay. I guess you need to look at the parts of the equation that make sense, and determine the relationship between them.

In this case, you have the number 7 and 21. You know that 21 will be the sum of the equation, the total. So now you just need to know what number, when multiplied by seven, will lead you to 21. That's easy - 7 times 3 is 21. So you know that the number in the brackets has to be 3, and from there it's easy to see that x must be 4.

Iam confused though - there's no symbol between the 7 and the brackets in that equation. Should there be one? It's been a while since I did algebra, I can't remember if you assume it's a multiplication when it looks like that.

It's just working backwards from the total.

No there is never a multipling symbol in algebra because it becomes too confusing. Especially when you have the letter x subsituting a number.

xx2 could be: x times 2 or x times x times 2. If you see what I'm saying.

 

[Abcinthia]

Guys I need help.

Could you tell me a good method so I can work out bracketed equations because I've tried and tried and failed. If you could help this would get on top of maths.

7(x-1)=21

I worked it out backwards the same way as HK.

We know 21 is made by 7 multiplied by x-1

So 21 divide by 7 = 3

Now 3 cannot be x because 1 was taken away.

Add the 1 to the 3 to get x.

3 + 1 = 4

4 = x

 

[Shekii]

Thanks too you guys watch me go ;P

8(x-1)=67
8x-8=67
8X = 75
x = 75/8 = 9.4.

 

[Boomerang]

You are doing great! I LOVE algebra!

 

[Mystic]

Guys I need help.

Could you tell me a good method so I can work out bracketed equations because I've tried and tried and failed. If you could help this would get on top of maths.

7(x-1)=21

divide each side by 7...x=4

 

[Kyle B]

divide each side by 7...x=4

Yea, that works. I added unnecessary steps there.