3. complete the square for 3x2 - 6x = 21.

x=1+2√2 or x=1−2√2

Step-by-step 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

answer: city needs 2.4 inches of rainfall more to match the record of 40 inches.

step-by-step explanation:

since we have given that

total annual rainfall a city record = 40 inches

this year, total rainfall recorded = 37.6 inches

number of inches of rainfall   is needed to match the record of 40 inches is given by

hence, city needs 2.4 inches of rainfall more to match the record of 40 inches.