Answer: (0,0), (-5,0), (2,0)
Explanation:
c(t)=4t⁴+12t³-40t²
1) t=0
c(t)= 4(0⁴)+12(0³)-40(0²)
c(t)=4(0)+12(0)-40(0²)
c(t)=0+0+0
c(t)=0
Thus (0,0)
2) c(t)=0
4t⁴+12t³-40t²=0
Divide both parts of the equation by 4:
t⁴+3t³-10t²=0
t²(t²+3t-10)=0
t²=0
t=0
Thus (0,0)
t²+3t-10=0
t²+(5t-2t)-10=0
(t²+5t)-(2t+10)=0
t(t+5)-2(t+5)=0
(t+5)(t-2)=0
t+5=0
t=-5
Thus (-5,0)
t-2=0
t=2
Thus (2,0)