How do you solve the equation #x^2-4.7x=-2.8# by completing the square?

Question

1769 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2018-06-26T21:16:59

Shown below

#x^2 - 4.7 x = -2.8 #

Take the coefficient of the #x# i.e. #-4.7 # half it, then square it, and add to both sides

#x^2 - 4.7x + (4.7/2)^2 = -2.8 + (4.7/2)^2 #

#x^2 -4.7x + 5.5225 = 2.7225 #

Then left hand side is a square polynomial:

#(x - 2.35 )^2 = 2.7225 #

Now sqrt both sides:

#x- 2.35 = pm sqrt(2.7225 ) #

#x = 2.35 pm 1.65 #

# x = { 0.7 , 4 } #