<span>x^2+4x-1/(x+2)^2=0
x^2 + 4x - 1 = 0
</span>

;
where a = 1, b = 4 and c = -1
To evaluate the probability that the lifespan will be between 1440 and 1465 hours will be given by:
P(1440<x<1465)
using the z-score formula we obtain:
z=(x-μ)/σ
where:
μ=1450
σ=8.5
hence
when x=1440
z=(1440-1450)/8.5
z=-1.18
P(z<-1.18)=0.1190
when x=1465
z=(1465-1450)/8.5
z=1.77
P(z<1.77)=0.9625
hence:
P(1440<x<1465)
=0.9625-0.1180
=0.8445
lim h→0 f(x + h) − f(x)h= limh→0x+h −4xh= limh→04x−4(x+h)x(x+h)= limh→04hhx(x + h)= limh→04x(x + h)=4x2.