The quadratic formula ?

Question

-10x2 + 11x + 24 = 20

-11 ±√281

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20

11 ±√281

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20

-11 ±√177

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-20

-11 ±√281

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18

2: -5x2 - 8x + 1 = 0

-4 ±√21

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5

-4 ±√20

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5

4 ±√21

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-6

-2 ±√21

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5

3: 6x2 - x - 5 = 0

{-3/2, 2}

{1, 5}

{1, -5/6}

{-2, 5/2}

4: -15x2 - 10x + 40 = 0

{-2, 2/3}

{4/3, -2}

{-1, 2}

{-2, 1/3}

5: 3x2 + 4 = -7x

{-1, -4/3}

{-1}

{1, 2}

{-3, 4}

Answer 1

If a x² + bx + c = 0 the x = { - b ± √[b² - 4 a c ] }  /  2a, use it.....( 2nd,1st, 3rd...