Anonymous
Anonymous asked in Education & ReferenceHomework Help · 3 weeks ago

Solve by substitution or addition?

Update:

I’m having trouble understanding this. I have looked through my notes but I really need help. 

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  • David
    Lv 7
    3 weeks ago

    By addition 3x = 18 and so x = 6 and by substitution y = 3

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  • 3 weeks ago

    Solving by adding the equations:

      x + 3y = 15

    2x -  3y =   3

    –––––––––––

    3x +  0y = 18

    3x = 18

    Divide both sides by 3

    x = 6 <––––––

    Substitute x = 6 into

    x + 3y = 15

    6 + 3y = 15

    subtract 6 from both sides

    3y =  9

    divide both sides by 3

    y = 3 <–––––

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  • 3 weeks ago

    By "addition" simultaneous solution:

    x + 3y = 15

    2x -3y = 3 add these two equations together.

    3x + 0 = 18

    x = 6; so that 3y = 15 - 6 = 9 and y = 3

    x = 6; y = 3 ANS

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  • 3 weeks ago

    By Substitution

    x = 15 - 3y 

    Hence 2(15 - 3y) - 3y = 3 

    30 - 6y - 3y = 3 

    30 - 9y = 3 

    9y = 27 

    y = 3 

    Hence 

    x + 3(3) = 15 

    x + 9 = 15 

    x = 6 

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  • Anonymous
    3 weeks ago

    If you have to ask strangers online how do you expect to pass a test? Talk to your teacher after class and tell him/her you do not understand. That is what a teacher is for, to TEACH you.

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