Question

4x^3 +35 = 21
How do I solve this equation?

Answer 1

-
`-\sqrt[3]{(7)/(2)}`

Explanation:

`4x^(3)+35=21`

`4x^(3)=21-35`

`4x^(3)=-14`

`x^(3)=-(14)/(4)` →
`-(7)/(2)`

`x=-\sqrt[3]{(7)/(2)}`

Answer 2

Explanation:

if you did not make any typos, then the equation is

4x³ + 35 = 21

well, you know how that is with solving equations : let's bring all terms with variables on one side, and all constant terms to the other side.

so, as first step we eliminate the + 35 on the left side by subtracting 35 on both sides :

4x³ = 21 - 35 = -14

next, we eliminate the multiplication factor 4 by dividing both sides by 4 :

x³ = -14/4 = -3.5

and now we pull the cubic root

`x = \sqrt[3]{ - 3.5}`

x = -1.518294486...

in contrast to square roots it is not a problem for cubic roots to have negative arguments, because a negative number to the power of 3 is again negative.

-a³ = -a×-a×-a = a²×-a = -a³