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# 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

- 1 decade agoFavorite 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 - 數學人Lv 51 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 41 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

- srLv 61 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