Maths question help ?

Solve by factorising x squared + 9x+20=0

15 Answers

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  • 4 months ago

    x^2 + 9x + 20 = 0

    (x + 4)(x + 5) = 0

    x + 4 =0 ,  x + 5 = 0 

    x = - 4, x = - 5 

    x = - 4, - 5 answer//

  • 4 months ago

    x^2 + 9x + 20 = 0

    x^2 + 5x + 4x + 20 = 0

    x(x + 5) + 4(x + 5) = 0

    (x + 5)(x + 4) = 0

    Solutions:

    x = -5

    x = -4

  • Anonymous
    4 months ago

    I did it in my mind the answer 

    Solutions:

    x = -5

    x = -4

  • Como
    Lv 7
    4 months ago

    ( x  +  5 ) ( x + 4 ) = 0

    x = - 5 , x = - 4

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  • sepia
    Lv 7
    4 months ago

    x^2 + 9x + 20 = 0

    (x + 5)(x + 4) = 0

    Solutions:

    x = -5

    x = -4

  • 4 months ago

    distribute 42 birds in 7 cages each contain an odd number?

  • Ian H
    Lv 7
    4 months ago

    Here is an explanation of how to do this example. 

    If you multiply out two factors such as (x + a)(x + b) you get  

    x^2 + (a + b)x + a*b,  

    so now compare that with your example 

    x^2 + 9x + 20 = 0 

    You need two numbers that add to make 9 and multiply to make 20. 

    That is easy, because 4 *5 = 20 and 4 + 5 = 9, so now you can write 

    x^2 + 9x + 20 = (x + 4)(x + 5) = 0 

    Either x + 4 = 0. which makes x = -4, or, 

    x + 5 = 0. which makes x = -5 

     

    You were expected to know this method already, so, I suggest that 

    you remember it now as it will be needed many times. 

  • 4 months ago

    You must be the laziest child in existence. Google it.

  • Anonymous
    4 months ago

    YOU ARE LAZY AND DISHONEST BY ASKING STRANGERS TO DO YOUR HOMEWORK. IF YOU TOLD YOUR TEACHER YOU DID IT YOU WOULD FAIL.

    And you SHOULD FAIL as you are cheating.

  • 4 months ago

    x^2 + 9x + 20 = 0

    (x + 5)(x + 4) = 0

    x = -5 or x = -4

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