Confused (1 Viewer)

[#Jess#]

can sum1 please answer this to tell me what they got. I am convinced that the answers are wrong and that my working is right.
When differentiating 4x(cubed) - 140x(squared) + 1000x
you get 12x(squared) - 280x + 1000
please solve this for x now
so: 0=12x(squared) - 280x + 1000

 

[Jago]

x= (70 + or - root 1900) / 6

 

[#Jess#]

how did you get that? i think my answer was around 11 or 12????

 

[placebo101]

he used the quadratic formula