Answer:
x=1+2√2 or x=1−2√2
Explanation:
Let's solve your equation step-by-step.
3x2−6x=21
Step 1: Since the coefficient of 3x^2 is 3, divide both sides by 3.
3x2−6x
3
=
21
3
x2−2x=7
Step 2: The coefficient of -2x is -2. Let b=-2.
Then we need to add (b/2)^2=1 to both sides to complete the square.
Add 1 to both sides.
x2−2x+1=7+1
x2−2x+1=8
Step 3: Factor left side.
(x−1)2=8
Step 4: Take square root.
x−1=±√8
Step 5: Add 1 to both sides.
x−1+1=1±√8
x=1±√8
x=1+2√2 or x=1−2√2