Question

solve each equation...
x^4-x=0
3x^4+18=21x^2
2x^4-26x^2-28=0
5x^4+50x^2+80=0
helpp pleasee!!!!!!!

Answer 1

for the 1st one take x as a common factor so you have

x(x^3 -1) = 0 so x = 0 or 1

Answer 2

3x^4+18=21x^2
3x^4-21x^2+18=0
Let y = x^2
3y^2 - 21y + 18 = 0
y = -1 or -6
x = ±i or ±(sqrt(6))i

Answer 3

2x^4-26x^2-28=0
x^4-13x^2-14=0
Let y = x^2
y^2 - 13y -14=0
y = -1 or 14
x = ±i or ±sqrt(14)

Answer 4

5x^4 + 50x^2 + 80 = 0
x^4 + 10x^2 + 16 = 0
Let y = x^2
y^2 + 10y + 16 = 0
y = -2 or -8
x = (sqrt(2))i or (2sqrt(2))i