Quadratic formula step by step

Is that supposed to be x² -4x -5 = 0 or x²-4-5=0 as written?  We'll do both.

As written it's

x²=9 so x=±3, no quadratic formula required.

Let's assume you meant

x² -4x - 5 = 0

So much temptation.  This factors as

(x-5)(x+1)=0 so roots x=5, x=-1.  But that didn't use the quadratic formula..

There's a shortcut to the quadratic formula called the Shakespeare Quadratic Formula (2b or -2b) that's useful when the linear term is even.

In that case x²-2bx+c has zeros at z=b±√(b²-c)

x = 2 ± √(4 - -5) = 2 ± √9 = 2 ± 3 = { -1 , 5 }

OK, let's do it like they want

x² - 4x - 5 = 0

We have a=1, b=-4, c=-5 and the quadratic formula

x=-1 or x=5

step-by-step explanation:

i found the life tables for the year 2012. 

life table of males at age 30. probability of dying between ages x and x+1

total population:  

29–30 . . . . . . . . . . . . 0.001030

30–31 . . . . . . . . . . . . 0.001061

males:  

29–30 . . . . . . . . . . . . 0.001420

30–31 . . . . . . . . . . . . 0.001448

white population

29–30 . . . . . . . . . . . . 0.001005

30–31 . . . . . . . . . . . . 0.001037

white males

29–30 . . . . . . . . . . . . 0.001372

30–31 . . . . . . . . . . . . 0.001399

non hispanic white population

29–30 . . . . . . . . . . . . 0.001083

30–31 . . . . . . . . . . . . 0.001116

non hispanic white males

29–30 . . . . . . . . . . . . 0.001477

30–31 . . . . . . . . . . . . 0.001503

jacob, non hispanic white male. 30 years old.

probability that jacob lives to be 30 years old. 

since the given probabilities are probabilities of dying, i think we simply subtract it from 1 to get the probability of living. we will use the probability of non hispanic white male.

                                          probability of living to be 30 y.o.

29 - 30 : 1 - 0.001477 = 0.998523

30 - 31 : 1 - 0.001503 = 0.998497