## 18jonea one year ago Solve the following expression for x: 81=3(x+y)^3 x = 243 - y x = 27 - y x = 3 - y x = 9 - y

1. 18jonea

@Michele_Laino

2. 18jonea

@Miracrown

3. anonymous

Ill try to help you but I'm not gonna put a answer if i think I'm wrong

4. mathstudent55

$$81=3(x+y)^3$$ Divide both sides by 3. What do you get?

5. 18jonea

27

6. 18jonea

what three am i taking away on the side though the exponent or the first 3

7. 18jonea

@mathstudent55

8. 18jonea

@Michele_Laino

9. Michele_Laino

hint: we can write this: $\Large {\left( {x + y} \right)^3} = \frac{{81}}{3} = 27$

10. 18jonea

ok then how do i get rid of the exponent

11. Michele_Laino

you have to take the third rooth of both sides

12. 18jonea

so how would i do that?

13. 18jonea

how do you takw the 3 root of both sides

14. mathstudent55

Correct. $$27=(x+y)^3$$ Now we notice that $$27 = 3^3$$, so we write: $$3^3 = (x + y)^3$$ If the third power of 3 equals the third power of x + y, then 3 must equal x + y. You can also take the cubic root of both sides. $$3 = x + y$$ There is only one step left. Subtract y from both sides.

15. 18jonea

so would it be 3-y=x @Michele_Laino or 9-y= x

16. Michele_Laino

it is the first one, namely x+y=3

17. 18jonea

ok

18. 18jonea

The following equation is used to determine the kinetic energy of an object: E=1/2mv^2. Solve for m:

19. 18jonea

@Michele_Laino

20. 18jonea

would it be 2E/ v^2

21. 18jonea

@mathstudent55

22. Michele_Laino

correct!

23. 18jonea

Thank you

24. 18jonea

Write an expression for the following description: 23 less than the product of x and 6. 6x-23 is that right

25. 18jonea

@Michele_Laino

26. Michele_Laino

yes!