詩思 asked in 科學及數學數學 · 1 decade ago

A F. 2 maths question (最佳解答全取10分)

Find the values of A, B and C in the following identitiy.

(2y+3)(y-4)+(y-2)(y+5)=Ay^2+By+C

Please show your working steps and explain your answer in details.

4 Answers

Rating
  • 1 decade ago
    Favorite Answer

    L.H.S(Left Hand Side)=(2y+3)(y-4)+(y-2)(y+5)

    =(2y^2-8y+3y-12)+(y^2+5y-2y-10)

    =2y^2-8y+3y-12+y^2+5y-2y-10

    =3y^2-2y-22

    By comparing like terms, we have

    Ay^2=3y^2

    A=3

    By=-2y

    B=-2

    C=-22

    希望你明啦

    Source(s): 自己
  • 1 decade ago

    (2y+3)(y-4)+(y-2)(y+5)=Ay^2+By+C

    2y^2-5y-12+y^2+3y-10=Ay^2+By+C

    3y^2-2y-22=Ay^2+By+C

    A=3,B=-2,C=-22

  • ?
    Lv 4
    1 decade ago

    (2y+3)(y-4)+(y-2)(y+5)=Ay^2+By+C

    2y^2 - 8y + 3y - 12 + y^2 - 2y + 5y - 10 = Ay^2+By+C

    3y^2 - 2y - 22 = Ay^2+By+C

    so, A = 3

    B = -2

    C = -22

  • sr
    Lv 6
    1 decade ago

    (2y+3)(y-4)+(y-2)(y+5)=Ay^2+By+C

    2y^2-5y-12+y^2+3y-10=Ay^2+By+C

    3y^2-2y-22=Ay^2+By+C

    A=3,B=-2,C=-22

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