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Question 1 of 4
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To find the roots of an equation in the form a x 2 + b x + c = 0 where a ≠ 0 , use the quadratic formula x = - b ± √ b 2 - 4 a c 2 a .
The equation x 2 + 6 x + 13 = 0 gives us a = 1 , b = 6 , and c = 13 .
x =
- b ± √ b 2 - 4 a c 2 a
Substitute in a = 1 , b = 6 , and c = 13 .
x =
- 6 ± √ 6 2 - 4 ( 1 ) ( 13 ) 2 ( 1 )
Simplify
x =
- 6 ± √ 6 2 - 4 ( 1 ) ( 13 ) 2
Simplify 6 2
x =
- 6 ± √ 36 - 4 ( 1 ) ( 13 ) 2
Multiply - 4 ( 1 ) ( 13 ) .
x =
- 6 ± √ 36 - 52 2
Subtract under the root.
x =
- 6 ± √ - 16 2
Separate out the √ - 1 from the root.
x =
- 6 ± √ - 1 × √ 16 2
Replace the √ - 1 remember √ - 1 = i
x =
- 6 ± i × √ 16 2
Simplify the root.
x =
- 6 ± i × 4 2
Rearrange - i × 4 so that the i is on the right-hand side in this term.
x =
- 6 ± 4 i 2
Divide both terms in the numerator by 2 .
x =
- 3 ± 2 i
x = - 3 + 2 i and x = - 3 - 2 i
Break into the two solutions.
Question 2 of 4
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To find the roots of an equation in the form a x 2 + b x + c = 0 where a ≠ 0 , use the quadratic formula x = - b ± √ b 2 - 4 a c 2 a .
The equation x 2 + 6 x + 13 = 0 gives us a = 1 , b = 2 , and c = 9 .
x =
- b ± √ b 2 - 4 a c 2 a
Substitute in a = 1 , b = 2 , and c = 9 .
x =
- 2 ± √ 2 2 - 4 ( 1 ) ( 9 ) 2 ( 1 )
Simplify
x =
- 2 ± √ 2 2 - 4 ( 1 ) ( 9 ) 2
Simplify 2 2
x =
- 2 ± √ 4 - 4 ( 1 ) ( 9 ) 2
Multiply - 4 ( 1 ) ( 9 ) .
x =
- 2 ± √ 4 - 36 2
Subtract under the root.
x =
- 2 ± √ - 32 2
Separate out the √ - 1 from the root.
x =
- 2 ± √ - 1 √ 32 2
Replace the √ - 1 remember √ - 1 = i
x =
- 2 ± i √ 32 2
Simplify using √ 32 = √ 16 × √ 2 .
x =
- 2 ± i √ 16 × √ 2 2
Simplify the root.
x =
- 2 ± i 4 √ 2 2
Rearrange i × 4 × √ 2 so that the i is in between the constant and the root.
x =
- 2 ± 4 i √ 2 2
Divide both terms in the numerator by 2 .
x =
- 1 ± 2 i √ 2
x = - 1 + 2 i √ 2 and x = - 1 - 2 i √ 2
Break into the two solutions.
Question 3 of 4
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To find the roots of an equation in the form a x 2 + b x + c = 0 where a ≠ 0 , use the quadratic formula x = - b ± √ b 2 - 4 a c 2 a .
The equation x 2 + 6 x + 13 = 0 gives us a = 1 , b = 5 , and c = 25 .
x =
- b ± √ b 2 - 4 a c 2 a
Substitute in a = 1 , b = 5 , and c = 25 .
x =
- 5 ± √ 5 2 - 4 ( 1 ) ( 25 ) 2 ( 1 )
Simplify
x =
- 5 ± √ 5 2 - 4 ( 1 ) ( 25 ) 2
Simplify 5 2
x =
- 5 ± √ 25 - 4 ( 1 ) ( 25 ) 2
Multiply - 4 ( 1 ) ( 25 ) .
x =
- 5 ± √ 25 - 100 2
Subtract under the root.
x =
- 5 ± √ - 75 2
Separate out the √ - 1 from the root.
x =
- 5 ± √ - 1 × √ 75 2
Replace the √ - 1 remember √ - 1 = i
x =
- 5 ± i × √ 25 × √ 3 2
Simplify the root using √ 75 = √ 25 × √ 3 .
x =
- 5 ± i × 5 × √ 3 2
Simplify the root.
x =
- 5 ± 5 i √ 3 2
Rearrange - i × 4 so that the i is in between the constant and the root.
x =
- 5 2 ± 5 i √ 3 2
Divide both terms in the numerator by 2 .
- 5 2 + 5 i √ 3 2 and - 5 2 - 5 i √ 3 2
Break into the two solutions.
Question 4 of 4
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To find the roots of an equation in the form a x 2 + b x + c = 0 where a ≠ 0 , use the quadratic formula x = - b ± √ b 2 - 4 a c 2 a .
Simplify the equation 3 x + 1 x = 2 by multiplying all of the terms by x . This gives 3 x 2 + 1 = 2 x . Now rearrange the equation into the form a x 2 + b x + c = 0 . This is 3 x 2 - 2 x + 1 = 0
The equation 3 x 2 - 2 x + 1 = 0 gives us a = 3 , b = - 2 , and c = 1 .
x =
- b ± √ b 2 - 4 a c 2 a
Substitute in a = 3 , b = - 2 , and c = 1 .
x =
- ( - 2 ) ± √ ( - 2 ) 2 - 4 ( 3 ) ( 1 ) 2 ( 3 )
Simplify - ( - 2 )
x =
2 ± √ ( - 2 ) 2 - 4 ( 3 ) ( 1 ) 2 ( 3 )
Simplify ( - 2 ) 2
x =
2 ± √ 4 - 4 ( 3 ) ( 1 ) 2 ( 3 )
Simplify - 4 ( 3 ) ( 1 )
x =
2 ± √ 4 - 12 2 ( 3 )
Subtract under the root.
x =
2 ± √ - 8 2 ( 3 )
Multiply 2 ( 3 )
x =
2 ± √ - 1 × √ 8 6
Separate out the √ - 1 from the root.
x =
2 ± i × √ 8 6
Replace the √ - 1 remember √ - 1 = i
x =
2 ± i × √ 4 × 2 6
Simplify the root.
x =
2 ± i × 2 √ 2 6
Rearrange i × 2 √ 2 so that the i is on the right-hand side in this term.
x =
2 6 ± 2 √ 2 6 i
Divide both terms in the numerator by 2 .
x =
1 3 ± √ 2 3 i
Simplify
x = 1 3 + √ 2 3 i and x = 1 3 - √ 2 3 i
Break into the two solutions.