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Can you Complete the Square?
In elementary algebra, completing the square is a technique for converting a quadratic polynomial of the form |
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Here's what I'm having trouble with:
Quadratic Formula; -b2 +- square root (b2 – 4ac) / 2a -5x2 – 3x – 3=0 I can't get the last part right : A quadratic equation with real or complex coefficients has two solutions, called roots. These two solutions may or may not be distinct, and they may or may not be real. The roots are given by the quadratic formula: In the above formula, the expression underneath the square root sign is called the discriminant of the quadratic equation, and is often represented using an upper case Greek Delta: Quadratic factorization |
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Given: -5x²-3x-3=0
Using the quadratic equation: -b±√(b²-4ac)/2a → 3±√(9-60)/-10 → 3±√(-51)/-10 You cannot take the square root of a negative value, the only way to express it is using the imaginary value i, where i=√(-1). So you factor in the radical. → 3±√(-1*51)/-10 → 3±√(-1)*√(51)/-10 → 3±√(51)i/-10 Now you can evaluate two separate answers which will have i. Your answer should look like a+bi, where a and b are the real part and i is the imaginary part. |
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Given: -5x²-3x-3=0 |
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Given: -5x²-3x-3=0 Here it is: 7x2 – 6x + 3 = 0 6±√(62 – 4 (7) (3)/2(7) 6±√(36-84)/2(7) 6±√(-48)/14 |
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If the number in the square root is negative it has the imaginary constant i
So just factor the -1 in the square root along with all the factors of 48. =√(-48) =√(48*-1) =√(2*24*-1) =√(2*2*12*-1) =√(2*2*2*6*-1) =√(2*2*2*2*3*-1) You have four factors of 2, one factor of 3, and one factor of -1. When you have two factors of the same number under a radical you can pull that number out, since √(4)=√(2*2)=2. (It's not limited to numbers, if you have two variables that are the same and are being multiplied together you can do the same thing) =2*2√(3*-1) =4√(3)i There's your imaginary part of the equation Having a negative value in the radical is the what the concept of imaginary values are about. You represent the √(-1) as i by factoring the radical. Also, having a positive or negative value in the denominator doesn't change anything about using the quadratic formula except sign changes. |
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