Use the quadratic formula to solve the equation: 0 = x2 + x - 20

(x-4)*(x+5) : x =4,-5

Step-by-step explanation:

a= 1

b= 1

c= -20

x1,2 = (-1+-(1 - (4*1*-20))^0.5)/2

x1,2 = (-1+-(1+80)^0.5)/2

x1,2 = (-1+-(81^0.5))/2

x1,2 =(-1+-9)/2

x1 = 8/2 = 4 x2 = -10/2 = -5

step-by-step explanation:

answer: .64

step-by-step explanation

set up the formula for standard deviation for this set of numbers, then simplify