How do you solve 3x ^(2/3) + x^(1/3) - 2 = 0?

1 Answer

x=8/27 and x=-1

Explanation:

From the given equation
3x^(2/3)+x^(1/3)-2=0

The solution goes like this

Let w=x^(1/3)

3x^(2/3)+x^(1/3)-2=0

we can write this equation this way

3(x^(1/3))^2+(x^(1/3))^1-2=0

also

3(w)^2+1*(w)^1-2=0

also let a=3 and b=1 and c=-2

w=(-b+-sqrt(b^2-4ac))/(2a)

w=(-1+-sqrt(1^2-4*3*(-2)))/(2*3)

w=(-1+-sqrt(1+24))/6

w=(-1+-sqrt25)/6

w=(-1+-5)/6

we have two values for w:

w_1=(-1+5)/6=4/6=2/3 and w_2=(-1-5)/6=-6/6=-1

But w=x^(1/3)

and x=w^3

Using w=2/3

x=w^3=(2/3)^3=8/27
x=8/27

Using w=-1

x=w^3=(-1)^3=-1

x=-1

check at x=8/27
3x^(2/3)+x^(1/3)-2=0
3(8/27)^(2/3)+(8/27)^(1/3)-2=0
3(4/9)+2/3-2=0
4/3+2/3-2=0
6/3-2=0
2-2=0
0=0
x=8/27 is a root

check at x=-1
3x^(2/3)+x^(1/3)-2=0
3(-1)^(2/3)+(-1)^(1/3)-2=0
3(1)-1-2=0
3-3=0
0=0

x=-1 is a root

God bless....I hope the explanation is useful.