Use the quadratic formula to solve : 0.7x^2-4.2x-0.7=0

Question

Use the quadratic formula to solve : 0.7x²-4.2x-0.7=0

The solution set is {_}

Answer 1

I would first simplify the equation by dividing through by 0.7, which gives:

 

x^2 - 6x -1 = 0

 

Then by the quadratic formula,

 

x = {-(-6) +/-sqrt[(-6)^2 - 4(1)(-1)]} / 2 = {6 +/-sqrt(40)] / 2 = 3 +/-sqrt(10)

 

You get two real roots:

 

x1 = 3 + sqrt(10)

x2 = 3 - sqrt(10)