## rainbow_rocks03 one year ago PLZ HELP NO DIRECT ANSWERS...will medal+fan. Which is equivalent to the expression shown when a>0 and b>0?

1. rainbow_rocks03

|dw:1440439527592:dw|

2. rainbow_rocks03

|dw:1440439634803:dw|

3. ikram002p

what have u tried ?

4. rainbow_rocks03

i dont understand this

5. ikram002p

ok :) so basically u can delete common terms in numerator and denominator according to this statement $$\Large \dfrac{a}{a}=1$$

6. rainbow_rocks03

ok

7. ikram002p

so what can u cancel from this ?|dw:1440440526567:dw|

8. ikram002p

for example |dw:1440440587931:dw|

9. ikram002p

what else can u cancel to make in the simplest form ?

10. rainbow_rocks03

the a's

11. ikram002p

yes one of them note that $$\Large a^2=a.a$$

12. ikram002p

|dw:1440440792739:dw| now whats left ?

13. ikram002p

PS : 21=3*7 & 35=5*7

14. rainbow_rocks03

3*7=21 & 5*7=35

15. rainbow_rocks03

so my answer would be d? @ikram002p

16. SolomonZelman

I don't think you need to know that $$\color{blue}{\left\{a,~b\right\}>0}$$.

17. rainbow_rocks03

@ikram002p ?

18. ikram002p

don't forget the minus sign -

19. rainbow_rocks03

oh so my answer would be c

20. SolomonZelman

Don't really know why the posted it, if b/b and a/a is 1 for any a even if was $$i\cdot \psi \cdot e \cdot \pi$$

21. ikram002p

we have canceled b from numerator

22. ikram002p

@SolomonZelman she need to know since a^2=a.a :D to be more accurate about the answer

23. SolomonZelman

a•a you mean by a.a ?

24. SolomonZelman

$$\large\color{black}{ \displaystyle \frac{ -21a^2b }{35ab} =\frac{(-3)\cdot7\cdot a \cdot a \cdot b}{5 \cdot 7\cdot a \cdot b} =\frac{(-3)\cdot a}{b}\times \frac{7\cdot a \cdot b}{7\cdot a \cdot b}}$$ i haven't crossed any numbers out, all I did so far is a rearrangement that is valid $$\forall~~a,b$$ (for all a and b)

25. ikram002p

yes which looks more nice :)

26. SolomonZelman

Thanks:) I mean even if there is any point in making a>0, though in by "b" we would never need such a condition.

27. SolomonZelman

oh, they should have said b and a are not 0, tho' ....

28. SolomonZelman

ok, now you know that because they said a and b >0. So Blank/Blank = 1, right?

29. SolomonZelman

u left with. ....

30. ikram002p

i agree with u but OP seems left :P