Question

X^2 - 2x = 15 how do I solve this quadratic method?
I am stuck on it.... please help
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Answer 1

(x - 5)(x + 3)

Explanation:

to solve x² - 2x = 15, we need to get all the terms on one side so we can solve the quadratic equation using factoring. to do this, we subtract 15 from both sides

x² - 2x = 15

- 15 -15

x² - 2x - 15 = 0

now we can factor. we need 2 numbers that when multiplied together give us -15, and when those 2 numbers are added together we get -2

because we have a -15, we can assume that one number must be negative and the other positive, as a negative times a postive is a negative.

we can use 3 and -5 as factors and test it out. we put x in front because we have an x²

(x - 5)(x + 3) < we can FOIL to check to see if this is correct. its not mandatory to check but when you arent sure of the answer you can FOIL it out

FOIL stands for: First, Outside, Inside, and Last terms

F: (x - 5)(x + 3) = x²

O: (x - 5)(x + 3) = -3x

I: (x - 5)(x + 3) = 5x

L: (x - 5)(x + 3) = -15

x² + 3x - 5x - 15 < subtract 3x from 5x

x² - 2x - 15

this checks out, so our answer is (x - 5)(x + 3)

Answer 2

x=5, x=-3

Explanation:

`x^2-2x=15\\x^2-2x-15=0\\`

next factor

look at 1st image attached

-5 and 3 multiply to be -15 and add to be -2

so
`(x-5) (x+3)`

to get what x equals set each part equal to 0 by flipping the signs

`x=5 x=-3`