### (8 March 2011) Chapter 4: Algebra... Help! What's Wrong?

Jane did the following:
• 3a + b = 3ab
• 2s + 4t = 6st
Do you think Jane is correct in her algebraic manipulations?
If yes, please write down examples to show that her answer is correct.

If not, explain to Jane her mistakes and help her to correct.

1. Nope, she is wrong.

3a+b=3a+b
2s+4t=2s+4t

The expressions are already simplified. So, she is wrong~~~

2. She is wrong.
3a + b should be 3a+b as it cannot be simplified further .
2s + 4t should be 2s + 4t as it cannot be simplified further .
Jane's answer is equivalent to 3*a*b as ab also means a*b and 6st will also mean 6*s*t.

3. Nope. As all expressions are already simplified.
3a + b = 3a+b.
a and b are different unknown numbers.
According to Jane's answer(3ab), the correct explanation is 3 times of a multiply by b,which is, 3*a*b.
The same thing for 2s +4t. Same explanation.

4. I think that she is wrong.

3a+b is already simplified. 3ab is actually 3 x ab which is wrong in this expression.

2s+4t is already simplified. 6st is 6 x st which is wrong.

5. Mark :) :( :&#39;( (^^^) :D :O :42: O:) :p 3:)3/08/2011 01:49:00 PM

She is wrong. 3a+b = 3a+b while 3ab=3xab or 3 x a x b. And the same goes for 2s + 4t.

6. She is wrong. 3a+b is 3*a+b but 3ab is 3*a*b.
Also, 2s+4t is equal to 2*s+4*t but 6st is 6*s*t.

7. I think she is wrong as the above expressions are already simplified and cannot be simplified further.Plus s and t are different numbers and cannot be mixed together.

8. Correction for Jane: 3a+b= 3a+b
2s+4t=2s+4t

9. She is wrong because ab and st means a*b and s*t but Jane is adding them so she should leave it as 3a+b and 2s+4t. Putting numbers beside unknowns or unknowns beside unknowns also causes people to mistake them as the coefficients of the unknown.

10. I think Jane is wrong.
The correct answers are: 3a+b=3a+b, 2s+4t=2s+4t.
3a+b and 2s+4t are expressions, not equations.
~Nina

11. This comment has been removed by the author.

12. No, she is not correct.
3ab is equal to 3*a*b, whereas it should equal to 3*a+1*b.
6st is equal to 6*s*t, whereas it should equal to 2*s+4*t.
She should leave the expressions as 3a+b and 2s+4t respectively as they cannot be simplified further.

13. She is wrong.
3a+b is equal to 3 sets of a plus b. But her answer is 3ab which is 3 sets of a times b which is wrong.

2s+4t is equal to 2 sets of s plus 4 sets of t. But her answer is 6st which is 6 sets of s times x.

These 2 question cannot be solved unless we know the variable.

14. 3a + b = 3ab
2s + 4t = 6st

3ab actually means 3*a*b which is different from 3*a+b
6st actually means 6*s*t which is different 2s+4t

Lovy Lim

15. ps. forgot to answer the main question...yup, that guy or girl is wrong

16. Nope, she is totally wrong.
3a*b=3*ab which is 3ab BUT 3a+b=3a+b
2s*4t=2*4*st which is 8st BUT 2s+4t=2s+4t

17. BTWFYI, I am Owen.
Sorry. :)

18. No,Jane is wrong. 3a is different from b so these two terms cannot be simplified as 3ab when added together.Similarly, 2s is also different from 4t so the coefficients and the variables cannot be add together.

Eg: let a be 3 and b be 4

1. 3a+b=3*3+4 2. 3ab=3*3*4
=9+4 =36
=13
The values are different.

Eg: let s be 5 and t be 6

1. 2s+4t=2*5+4*6 2. 6st=6*5*6
=10+24 =180
=34
The values are different.