+0  
 
0
459
1
avatar

 

 

please slove for the variable, and make the world smile again?

x^4+4x^2−32=0

 

t^6=8−t^3

thank you for your greatness

 Apr 13, 2016
 #1
avatar
0

Solve for x:
x^4+4 x^2-32 = 0

Substitute y = x^2:
y^2+4 y-32 = 0

The left hand side factors into a product with two terms:
(y-4) (y+8) = 0

Split into two equations:
y-4 = 0 or y+8 = 0

Add 4 to both sides:
y = 4 or y+8 = 0

Substitute back for y = x^2:
x^2 = 4 or y+8 = 0

Take the square root of both sides:
x = 2 or x = -2 or y+8 = 0

Subtract 8 from both sides:
x = 2 or x = -2 or y = -8

Substitute back for y = x^2:
x = 2 or x = -2 or x^2 = -8

Take the square root of both sides:
Answer: |  x = 2    or    x = -2    or    x = (2 i) sqrt(2)    or    x = (-2 i) sqrt(2)

 

Solve for t over the real numbers:
t^6 = 8-t^3

Subtract 8-t^3 from both sides:
t^6+t^3-8 = 0

Substitute x = t^3:
x^2+x-8 = 0

Add 8 to both sides:
x^2+x = 8

Add 1/4 to both sides:
x^2+x+1/4 = 33/4

Write the left hand side as a square:
(x+1/2)^2 = 33/4

Take the square root of both sides:
x+1/2 = sqrt(33)/2 or x+1/2 = -sqrt(33)/2

Subtract 1/2 from both sides:
x = sqrt(33)/2-1/2 or x+1/2 = -sqrt(33)/2

Substitute back for x = t^3:
t^3 = sqrt(33)/2-1/2 or x+1/2 = -sqrt(33)/2

Take cube roots of both sides:
t = (sqrt(33)/2-1/2)^(1/3) or x+1/2 = -sqrt(33)/2

Subtract 1/2 from both sides:
t = (sqrt(33)/2-1/2)^(1/3) or x = -1/2-sqrt(33)/2

Substitute back for x = t^3:
t = (sqrt(33)/2-1/2)^(1/3) or t^3 = -1/2-sqrt(33)/2

Take cube roots of both sides:
Answer: |  t = (sqrt(33)/2-1/2)^(1/3)    or    t = -(1/2+sqrt(33)/2)^(1/3

 Apr 13, 2016

3 Online Users

avatar