Question #25ae4

2 Answers
Oct 28, 2017

5,[-5+-5isqrt(3)]/2

Explanation:

Given,z^3-125 = 0
rArr z^3-5^3 =0
rArr (z-5)(z^2+5z+25)=0
rArr (z-5)=0,(z^2+5z+25)=0
rArr z=5,z=[-5+-sqrt(5^2-4xx25xx1)]/(2xx1)
rArr z=5,z=[-5+-sqrt(-75)]/(2)
rArr z=5,[-5+-5isqrt(3)]/2

Oct 28, 2017

z=5

Explanation:

z^3-125=0

:.z^3=125

cube root both sides

:.root3(z^3)=root3(125)

:.root3(z*z*z)=root3(5*5*5)

:.root3(5)xxroot3(5)xxroot3(5)=5

:.root3(z)xxroot3(z)xxroot3(z)=z

:.z=5