Question

What is the first step in the solution of 3x2+6x=12 by completing the square?

A: r3+r=2
B: r2+2r=4
C: 3r2+6r+9=12+9
D: 3r2+6r+36=12+36

Answer 1

• 3x²+6x=12

Divide all terms by a i.e 3

We get

• x²+2x=4

Or

• r²+2r=4

Option B is correct

Answer 2

B: r² + 2r = 4

Step-by-step explanation:

`\rightarrow \sf 3x^2+6x=12`

divide both sides by 3

`\rightarrow \sf x^2+2x=4` ← This is the result of the first step.

factor out the common term

`\rightarrow \sf x(x+2) = 4`

set to 0

`\rightarrow \sf x = 4, \ x+2 = 4`

simplify

`\rightarrow \sf x = 4, \ x= 2`