Help with algebra PLZZZ 10 pts best answer!!!?

Question

ARGGGGGGGG i cant figure this out ok i have no clue how to do this, so plzzzzz plzzzz help me out with a couple so i can have somethin to go by for the rest of my h/w and plz show your work step by step


1. x^2 + 0.65 = 1.8x

2. x^2 + 5x = 2x +5

3. 5x^2 + 13x + 7 = 0

4. -4x^2 + 20x + 39 = 0

plz put your answer in S={#, #} and have your numbers rounded to the first 2 decimal places..thx!!

plz help me with at least 2..i cant figure it out with my book cuz my teacher taught us the way she was taught how to do it, and in our notes we didnt do anything like this, all we did were REAL simple ones that i easily could do and werent set up to where i had to transform before i completed the square.


THaNK YoU SO MUCH
10 pts BA!

Answer 1

Do you have to factor or complete the square? Factoring is sometimes easier to do, but it depends on the problem itself.

We can do the first one by completing the square. First get the x-terms on one side and the constants on the other:
x^2 + 0.65 = 1.8x
x^2 - 1.8x = 0.65

Next, take half of the constant of the linear term and square it. Then take that number and add it to both sides:
x^2 - 1.8x + 0.81 = 0.65 + 0.81

Factor the left and add the right side:
(x - 0.9)^2 = 1.44

Then, take the square root of both sides and solve as usual:
x - 0.9 = +/- 1.2
x = 2.1, -0.3

The second is similar:

x^2 + 5x = 2x + 5
x^2 + 3x = 5
x^2 + 3x + 2.25 = 5 + 2.25
(x + 1.5)^2 = 7.25
x + 1.5 = +/- sqrt(7.25)
x = -1.5 +/- sqrt(7.25) <---You can use your calculator to figure that one out.

5x^2 + 13x + 7 = 0
x^2 + 13x/5 + 7/5 = 0
x^2 + 13x/5 = -7/5
x^2 + 13x/5 + 169/100 = -7/5 + 169/100
(x + 13/10)^2 = 29/100
x + 13/10 = +/-sqrt(29)/10
x = [-13 +/- sqrt(29)] / 10

-4x^2 + 20x + 39 = 0
x^2 - 5x - 39/4 = 0
x^2 - 5x = 39/4
x^2 - 5x + 6.25 = 39/4 + 6.25
(x - 2.5)^2 = 16
x - 2.5 = +/- 4
x = 2.5 +/- 4
x = 6.5, -2.5