Solve by completing the square: -2x squared -20x-6=0?

Question

Please help I'm desprate!!!!I have the worst teacher on the planet!

Answer 1

This is the original problem. -2x^2 – 20x – 6 = 0
Move the loose number over to the other side. -2x^2 – 20x = 6
2x^2 +20x = -6
x^2 +10x = -3
Take half of the coefficient (don't forget the sign!) of the x-term, and square it. Add this square to both sides of the equation. (10/2)^2 =25
x^2+10x + 25 = -3 +25
(x + 5)^2 = 22
x + 5 = sqrt(22)
x = +/- sqrt(22) - 5

bee made a mistake with her signs

Answer 2

omg! i actually remember this!!! wow, anyways,
first you have to establish your 1st step: ax squared + bx + c = 0.

so, that means you have you equation a = -2, b = -20, and c = -6


0 is a universal number just so you know.


Second step:

now that you have established it, you need to plug in your formula. this is the one you are going to use:

-b + or - the square root of b squared - 4(a)(c)
divided by
2a

basicly you have:

-20 + or - the square root of -20 squared -4(-2)(-6)
divided by
2(-2)


Then you do the square root part and the equation should look like this after you simplified it more (this is step by step):

1) -20 + or - the square root of -20 squared - 4(-2)(-6)
divided by
2(-2)
*fyi!!! a negative times a negative is always positive:

2) -20 + or - the square root of 400 - 8(-6)
divided by
2(-2)

3) -20 + or - the square root of 400 - (-48)
divided by
2(-2)

4) -20 + or - the square root of 352
divided by
2(-2)
*When you square root 352, you end up w/ a decimal. I rounded to the nearest hundreth. Check w/ your teacher or in the instructions about where you should round to. Most would say the hundreth

5) -20 + or - 18.76
divided by
2 (-2)

*+ or - would work in both situations. So i'll do both for you.

6)-20 + 18.76
divided by
2(-2)

or

-20 - 18.76
divided by
2(-2)

7) -1.24
divided by
2(-2)

or

-38.76
divided by
2(-2)


8)-1.24
divided by
-4

or

-38.76
divided by
-4

9)Answers: x=0.31 and x=9.69

10) Check your answers! I'll leave that part to you.

If you did not understand what I explained in the last 15 minutes of typing, you need to go ask you teacher when they have extra help available.
peace out.

Answer 3

-2x^2-20x-6

start out by dividing everything by -2. you need to get rid of the number before x-squared

X^2+10x+3=0

Subtract +3 from both sides.

X^2+10x= -3

now, take the coefficient of b (which in this case is 10) and divide it by 2. then square it and add THAT number to both sides.

10/2=5^2=25 so now we have

X^2+10x+25=3+25
X^2+10x+25=28

simplify your quadratic. we've forced it to be a perfect square.

(X+5)(X=5)=28

take the square root of both sides. the square root of (x+5)^2 is (X+5).

(X+5)=(the sq. rt. of 28)

simplify..

X+5=2(square root of 7)

solve for X

x should equal 5 (plus or minus) 2(square root of 7)

Answer 4

well..........i got 10x