The solutions to x2 - 8x = 24:
First, get all terms to one side by subtracting 24 from both sides:
x2 - 8x - 24 = 0
Now, try factoring this -- but it doesn't factor nicely -- so you can graph this, use the quadratic formula or complete the square -- I'm choosing to complete the square.
Back to moving the number back to the right side:
x2 - 8x = 24
Since the coefficient of the x-squared term is 1, work with the coefficient of the x-term -- -8
Completing the square is a three step process:
-- first, divide the coefficient of the x-term by 2: -8 / 2 = -4
-- second, square this number: (-4)2 = 16
-- third, add this number to both sides of the problem:
x2 - 8x + 16 = 24 + 16
Factor the left side, simplify the right side:
(x - 4)(x - 4) = 40
(x - 4)2 = 40
Take the square root of both sides:
either x - 4 = sqrt(40) or x - 4 = - sqrt(40)
so either x = 4 + sqrt(40) or x = 4 - sqrt(40)
solve for x:
x^2-8 x=24
Add 16 to both sides:
x^2-8 x+16=40
Write the left hand side as a square:
(x-4)^2=40
Take the square root of both sides:
x-4=2 sqrt(10) or x-4=-2 sqrt(10)
Add 4 to both sides:
x=4+2 sqrt(10) or x-4=-2 sqrt(10)
Add 4 to both sides:
Answer: | x=4+2 sqrt(10) or x=4-2 sqrt(10)
The solutions to x2 - 8x = 24:
First, get all terms to one side by subtracting 24 from both sides:
x2 - 8x - 24 = 0
Now, try factoring this -- but it doesn't factor nicely -- so you can graph this, use the quadratic formula or complete the square -- I'm choosing to complete the square.
Back to moving the number back to the right side:
x2 - 8x = 24
Since the coefficient of the x-squared term is 1, work with the coefficient of the x-term -- -8
Completing the square is a three step process:
-- first, divide the coefficient of the x-term by 2: -8 / 2 = -4
-- second, square this number: (-4)2 = 16
-- third, add this number to both sides of the problem:
x2 - 8x + 16 = 24 + 16
Factor the left side, simplify the right side:
(x - 4)(x - 4) = 40
(x - 4)2 = 40
Take the square root of both sides:
either x - 4 = sqrt(40) or x - 4 = - sqrt(40)
so either x = 4 + sqrt(40) or x = 4 - sqrt(40)