How do you solve by completing the square for x^2+ 3/2x = 3?

2 Answers
Mar 20, 2018

x=+sqrt(57/16)-3/4 = 1.1374

or

x=-sqrt(57/16)-3/4 = -2.6374

Explanation:

x^2+3/2x=3

=> x^2+3/2x-3=0

=> (x+3/4)^2-(3/4)^2-3=0

=> (x+3/4)^2-(9/16)-3=0

=> (x+3/4)^2-(9/16)-(48/16)=0

=> (x+3/4)^2-(57/16)=0

=> (x+3/4)^2=57/16

=> x+3/4=+-sqrt(57/16)

=> x=+-sqrt(57/16)-3/4

Therefore, x is either

x=+sqrt(57/16)-3/4 = 1.1374

x=-sqrt(57/16)-3/4 = -2.6374

Mar 20, 2018

x=(-3+-sqrt57)/4

Explanation:

x^2+3/2 x =3

Add (3/4)^2 both sides.

=> x^2+3/2x+(3/4)^2 = 3+(3/4)^2

=> (x)^2 + 2xx x xx3/4 + (3/4)^2 = 3+9/16

=> (x+3/4)^2 = 57/16

=> x+3/4=(+-sqrt57)/4

=> x=(+-sqrt57)/4 - 3/4

=> x=(-3+-sqrt57)/4