Question

Someone please help me out!! I’m struggling

Answer 1

Step 1: -15

Step 2: b = 12, c = 36

Step 3-4: x² + 12x + 36 = -15 + 36, which simples to (x + 6)² = 21

If there is a step that has you solve for x, it should be -6 + √21 or -6 - √21.

Explanation:

Step 1 is pretty simple. All we have to do is subtract 15 from 0 to get the first blank.

x² + 12x = 0 - 15

x² + 12x = -15

Step 2:

b is the coefficient on x, which is 12.

Then, use the formula mentioned:

`c = ( (b)/(2))^(2) \\ c = ( (12)/(2) )^(2) \\ c ={6}^(2) \\ c = 36`

As a result of that, c is 36.

Now to substitute and simplify. (Steps 3-4)

x² + 12x + 36 = -15 + 36

To factor an equation, think about it like this: Find two numbers that add to the coefficient of x, and multiply to the constant. So what two numbers add to 12, and multiply to 36? That would be 6 & 6 (6 + 6 = 12; 6 × 6 = 36).

(x + 6)² = -15 + 36

Add 36 to -15 to get 21.

(x + 6)² = 21

That should solve steps 1-4, but I will go on ahead and give the final answer to the entire problem.

(x + 6)² = 21

Yes, you are about see what I just factored be expanded back over again. It's part of the process.

x² + 12x + 36 = 21

Now subtract 21 from both sides.

x² + 12x + 36 - 21 = 21 - 21

x² + 12x + 15 = 0

Now onto the hard part of this: the quadratic formula. a = (the understood) 1, b = 12, and c = 15.

x = (-b ± √b² - 4ac)/2a

x = -12 ± √12² - 4(15)/2

x = -12 ± √144 - 60/2

x = -12 ± ✓84/2

x = -6 + √21 or -6 - √21

Answer 2

This is called "completing the square"

It is a technique to solve a quadratic equation. It involves "moving all

of the constants to the right" , then doing a "move" on the left hand side. This move "creates a perfect square".. This is done by taking 1/f of the "B" term and squaring it... this will "un-balance" the sides of the equation... to balance it out you have to "add" some stuff to the right hand side... when done the left side will be "a perfect square" .. last step will be take the square root of both sides.

Explanation:

`x^2 + 12x + 15 = 0`

`x^2 + 12x + 15 -15 = -15`

`x^2 + 12x = -15`

`b = 12 ... (1/2 b)^2 = 6^2 = 36`

`x^2 + 12x + 36 = -15 + 36`

`x^2 + 12x + 36 = 21`

`(x+ 6)^2 = 21`

`√((x+ 6)^2 ) =` ±
`√(21)`

`x+ 6`= ±
`√(21)`

x = -6 ±
`√(21)`