Solve by using the quadratic formula. x^2 = 5x + 8?

Question

Solve by using the quadratic formula. x^2 = 5x + 8

Answer 1

First, get it all on one side" x^2-5x-8=0
Then a=1, b=-5 and c=-8. Go for it.

Answer 2

X^2 = 5x +8 can be solved by moving things around.

X*X - 8 = X+X+X+X+X So now, all we need is some number, that when multiplied by itself, plus 8, is the same as 5 times itself. And at this point I'd probably try brute force. I tried using a spreadsheet, but it doesn't seem to work.

Or let's try a different answer X^2 - 8 - X*5 = 0 would also work. Then I just tried using a spreadsheet until the formula produced 0. For that, I get 6.275 for X. Hope this works.

Maybe my math is all screwed up, but I don't know where the other people answering are getting A, B and C.

Answer 3

It would be x^2-5x-8=0 with A=1, B=-5 and C=-8. I can't remember the quadratic formula off the top of my head, but if you can get the formula, you can solve it by plugging in the numbers from my answer.

Answer 4

x² = 5x + 8

First rewrite the equation in the form of decreasing orders of x
x ² - 5x - 8 =0

This is of the Form
A x² + B x + C = 0 where: A,B & C are constant coefficients of x.

(1)x² + (- 5)x + (- 8) = 0

A = 1
B = -5
C = -8

Use the formula:

x = {-B ± √ [(B)² - 4(AC)]} / 2A

x = {-(-5) ± √ [(-5)² - 4(1)(-8)]} / 2(1)

x = {(5) ± √ [(25) + (32)]} / 2(1)

x = {(5) ± √ (57)} / 2 Compute for the two roots.

_____________________
x = {(5) + √ (57)} / 2
x = { 5 + 7.55} / 2 = 6.275 ≈ 6.28

x = {(5) - √ (57)} / 2
x = { 5 - 7.55} / 2 = - 1.275 ≈ -1.28


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Answer 5

x^2 = 5x + 8
x^2 - 5x - 8 = 5x + 8 - 5x -8
0 = (1)X^2 + (-5)x + (-8)

x = (-b +/- sqrt(b^2-4ac))/2a {hope I didn't get that wrong }

x = (5 +/- sqrt(25-(-32)))/2
= (5 +/- sqrt(57))/2
= (5 +/- 7.55) / 2
= 6.275 and -1.275

Now...assuming you had any class work that talked about using the Quadratic formula, this should have been rather simple. If you just wanted to confirm your answer...there you go. If you had no idea what to do...ask tomorrow to have it explained in detail.

Answer 6

-5x + x^2 + 8 = 0

Answer 7

12

Answer 8

1st. you have to make it to standard form. "ax^2+bx+c.
Therefore, subtract x^2 from both sides.
your new answer would be -x^2+5x+8.
remember, you cant have a (-) coefficient, so divide by -1.
new answer would be x^2-5x-8.
the quadratic formula is -b+/- (rad) b^2-4ac.
so, A=1,B=-5,C=-8.
so plug in your answers.
and solve.. if u need more help. contact me..

Answer 9

X^2=5x+8

x^2-5x-8=0 (x-4)(x+2)-3x=0


x1=4 x2=-2 x3=0

Answer 10

x^2-5x-8=0
x=-b+or-sqrtb^2-4ac/2a
x=-5+or-5^2-4(1)(-8)/2(1)
x=-5+or-sqrt25+32/2
X=-5+or-sqrt57/2
x=-5-sqrt57/2 or x=-5+sqrt57/2
sorry i cud not compute for the sqrt of 57
i dont have calculator