Equation: x2 + 8x + 12 = 0
Worded: x squared plus eight x plus twelve equals zero.
There is a twist: Do this by
-Factoring (Demonstrate how to solve your equation by factoring)
-Completing the Square (demonstrate how to solve your equation by completing the square)
-The Quad Formula (demonstrate how to solve the equation using the quadratic formula)
And that's it.
Worded: x squared plus eight x plus twelve equals zero.
There is a twist: Do this by
-Factoring (Demonstrate how to solve your equation by factoring)
-Completing the Square (demonstrate how to solve your equation by completing the square)
-The Quad Formula (demonstrate how to solve the equation using the quadratic formula)
And that's it.
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x^2 + 8x + 12 = 0
First by factoring:
(x + 6) * (x + 2) = 0
So, x = -6 and x = -2
Next, by completing the square, first move the 12 over
x^2 + 8x = -12
Divide 8 in half to get 4, square it to get 16, and add this to each side:
x^2 + 8x + 16 = 4
Factor to find the squared term:
(x + 4)^2 = 4
Square root (remembering both roots):
x + 4 = 2 and x = 4 = -2
Solving for x:
x = -2 and x = -6
By the quadratic formula, using a = 1, b = 8, and c = 12:
-8 +/- sqrt((8)^2 - 4(1)(12)) / 2(1)
-8 +/- sqrt(64 - 48) / 2
-8 +/- sqrt(16) / 2
The two solutions are:
x = (-8 + 4)/2 and x = (-8 - 4)/2, which are:
x = -2 and x = -6
First by factoring:
(x + 6) * (x + 2) = 0
So, x = -6 and x = -2
Next, by completing the square, first move the 12 over
x^2 + 8x = -12
Divide 8 in half to get 4, square it to get 16, and add this to each side:
x^2 + 8x + 16 = 4
Factor to find the squared term:
(x + 4)^2 = 4
Square root (remembering both roots):
x + 4 = 2 and x = 4 = -2
Solving for x:
x = -2 and x = -6
By the quadratic formula, using a = 1, b = 8, and c = 12:
-8 +/- sqrt((8)^2 - 4(1)(12)) / 2(1)
-8 +/- sqrt(64 - 48) / 2
-8 +/- sqrt(16) / 2
The two solutions are:
x = (-8 + 4)/2 and x = (-8 - 4)/2, which are:
x = -2 and x = -6
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Factoring:
(x + 6)(x + 2)=0
So, by the zero factor property: x + 6 = 0 and x + 2 = 0. Which means x = -6 and x = -2.
Completing the square:
Get the x-terms on one side
x2 + 8x = -12
Add (8/2)^2 to both sides to complete the square on the left side. (8/2)^2 = (4)^2 = 16
x2 + 8x + 16 = -12 + 16
(x + 4)^2 = 4
Take the square root of both sides to get
x + 4 = +-2
This gives x = -4 +- 2, which means x = -4 + 2 and x = -4 - 2, which means x = -2 and x = -6
The Quad Formula:
A = 1, B = 8 and C = 12, so
x =[ -8 +- squareroot(8^2 - 4*1*12)] / 2(1)
x = [-8 +- squareroot(64 - 48)] / 2
x = [-8 +- 4] / 2
So, x = -12/2 = -6 and x = -4/2 = -2
(x + 6)(x + 2)=0
So, by the zero factor property: x + 6 = 0 and x + 2 = 0. Which means x = -6 and x = -2.
Completing the square:
Get the x-terms on one side
x2 + 8x = -12
Add (8/2)^2 to both sides to complete the square on the left side. (8/2)^2 = (4)^2 = 16
x2 + 8x + 16 = -12 + 16
(x + 4)^2 = 4
Take the square root of both sides to get
x + 4 = +-2
This gives x = -4 +- 2, which means x = -4 + 2 and x = -4 - 2, which means x = -2 and x = -6
The Quad Formula:
A = 1, B = 8 and C = 12, so
x =[ -8 +- squareroot(8^2 - 4*1*12)] / 2(1)
x = [-8 +- squareroot(64 - 48)] / 2
x = [-8 +- 4] / 2
So, x = -12/2 = -6 and x = -4/2 = -2
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Factoring: (x+6)(x+2)
x=-6,-2
Completing the square:
x^2 + 8x = -12
Take half of 8, 4. Square it and add it to both sides
x^2 + 8x +16 = -12+16
(x+4)(x+4)=4
Squre root both sides
x+4=+/- 2
x=-4 +/- 2
x=-6,-2
Quad Formula:
a=1
b=8
c=12
-8 +/- Sqroot (8^2-(4*1*12))/2(1)
-8 +/- Sqroot (64-48)/2
-8 +/- Sqroot (16)/2
(-8 +/- 4)/2
-8+4=-4/2=-2
-8-4=-12/2=-6
x=-6,-2
Completing the square:
x^2 + 8x = -12
Take half of 8, 4. Square it and add it to both sides
x^2 + 8x +16 = -12+16
(x+4)(x+4)=4
Squre root both sides
x+4=+/- 2
x=-4 +/- 2
x=-6,-2
Quad Formula:
a=1
b=8
c=12
-8 +/- Sqroot (8^2-(4*1*12))/2(1)
-8 +/- Sqroot (64-48)/2
-8 +/- Sqroot (16)/2
(-8 +/- 4)/2
-8+4=-4/2=-2
-8-4=-12/2=-6