Question 175331
You are trying to get the vertex. In order to do this you need to complete the square f(x)=5x^2-20x+3.Set f(x)=0

0=5x^2-20x+3
Subtract 3 from both sides

-3=5x^2-20x
Factor out the 5 on the right hand side of the equation

-3=5(x^2-4x

divide the 4 by 2 and then square it.

-3=5(x^2-4x+4)

since you added an additonal 20 on the right side -don't forget to multiply the 4 you just added by 5

-3+20=5(x-2)^2

17/5=(x-2)^2

take the square root of each side 17/5sq rt=x-2

sqrt85/5=x-2

add two to both sides

x=2sqrt85/5