x(x + 1) = 0 3x + 6 = 0 4x – 2 = 3x – 5 x(x – 40 ) + 5x = 20 3x – 6(x – 3) + 4(x + 5)=11

Question

x(x + 1) = 0
3x + 6 = 0
4x – 2 = 3x – 5
x(x – 40 ) + 5x = 20
3x – 6(x – 3) + 4(x + 5)=11

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Verity 6 years 2020-11-21T13:03:23+00:00 2 Answers 72 views 0

Answers ( )

  1. minhkhang
    0
    2020-11-21T13:04:30+00:00
    Reply

    Đáp án:

     1) x(x+1)=0

    ⇒x=0 hoặc x+1=0

                       x=-1

    Vậy x=-1

    2)3x+6=0

       3x=-6

        x=-2 

    Vậy x=-2

    3)4x-2=3x-5

       4x-3x=-5+2

        x=-3

    Vậy x=-3

    3)x(x-40)+5x=20

       x²-40x+5x=20

       x²-35x=20

       x(x-35)=20

    ⇒ x=20 hoặc x-35=20

                          x=55 

    Vậy x=55

    4)3x – 6(x – 3) + 4(x + 5)=11

     

       3x – ( 6x + 18) + (4x + 20) = 11

        3x – 6x – 18 + 4x + 20 = 11

        ( 3x – 6x + 4x) – ( 18 – 20) = 11

                                          x + 2 = 11

                                          x = 11 – 2

                                          x = 9

    Vậy x = 9.

  2. Edana
    0
    2020-11-21T13:04:40+00:00
    Reply

    a, x(x + 1)= 0

       => x= 0 hoặc x+ 1= 0

                             x = 0 – 1

                             x = -1

    Vậy x ∈ { 0; -1 }.

    b, 3x + 6 = 0

        3x = -6

         x= -6 : 3

         x= -2

    Vậy x= -2.

    c, 4x – 2 = 3x -5 

       4x – 3x = -5 + 2

                x = -3

    Vậy x = -3.

    e, 3x – 6(x- 3) + 4(x+5) = 11

        3x – ( 6x + 18) + (4x + 20) = 11

        3x – 6x – 18 + 4x + 20 = 11

        ( 3x – 6x + 4x) – ( 18 – 20) = 11

                                          x + 2 = 11

                                          x = 11 – 2

                                          x = 9

    Vậy x = 9.

    (Câu d mik ko bt làm, xl bạn)

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