Question 137100
cube means raised to the power of 3. So yes, cube really affects the problem.

Let's look at the first one.
Given: {{{x^3 + 3x = 47}}} show the value is between 3 and 4.

Substitute in x = 3
{{{3^3 + 3*3}}} = {{{27+9}}} = {{{36}}} which is less than 47

Now use 4
{{{4^3 + 4*3}}} = {{{64+12}}} = {{{76}}} which greater than 47. So x lies beween 3 and 4.

Make sense?