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? asked in Education & ReferenceHomework Help · 9 years ago

Math help? (1 Problem)?

What two numbers multiply to give you -20, and add up to give you -1?

I'll give you an example

-8 and 15 would be

-3 + -5 = -8

-3 x -5 = 15

For the life of me, I cannot figure out the problem. Help?

Update:

fuuuuuuuuuuuuu

2 Answers

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  • ?
    Lv 6
    9 years ago
    Favorite Answer

    >.<

    let:

    x = 1st no.

    y = 2nd no.

    xy = -20 -------> eq.1

    x + y = -1 -------> eq.2

    so..

    x = -1 - y

    Plugin x to eq.1:

    y(-1 - y) = -20

    -y - y^2 = -20

    y^2 + y - 20 = 0

    (y - 4)(y + 5) = 0 <-------- by factorization

    so..

    y - 4 = 0

    y = 4

    and

    y + 5 = 0

    y = -5

    so..

    xy = -20

    x = -20/4

    x = -5

    xy = -20

    x = -20/(-5)

    x = 4

    Therefore the two numbers are 4 and -5.

  • Anonymous
    9 years ago

    90000

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