## anonymous one year ago Solve x3 = 64 over 27. ±8 over 3 8 over 3 ±4 over 3 4 over 3

1. anonymous

@phi

2. phi

3. anonymous

this isnt the one that needs checking

4. phi

x^3 means x*x*x so you could check if the answer times itself 3 times gives 64/27

5. phi

I am suggesting a way to decide what the answer is. one way is to check each of the 4 possible answers. only one of them should "work"

6. phi

the other way to answer the question is to "solve for x" but that involves finding cube roots.

7. anonymous

hmmm

8. anonymous

let me look rlly fast

9. anonymous

im not sure

10. phi

let's test x= 8/3 what is $\frac{8}{3} \cdot \frac{8}{3} \cdot \frac{8}{3}$ multiply top times top and bottom times bottom

11. anonymous

512/27?

12. anonymous

@phi is that it

13. phi

yes and 512/27 is not 64/27 in other words, 8/3 (and also -8/3) is not the answer the other two choices are 4/3 and $$\pm$$ 4/3 the only difference is the second choice includes -4/3 but -4/3 * -4/3 * -4/3= -64/27 it is negative and we want +64/27 that means the only answer that works is 4/3