A,B,C are constants , find A,B,C 1.If (x+2)(Cx+B)=3x^2+4x+A is an identity 2.If A(2x+1)^2-3Bx+(B-C)=(4x-1)(x-4) is an identity?

1.
(x + 2)(Cx + B) ≡ 3x² + 4x + A

Put x = -2.
0 = 3(4) + 4(-2) + A
A = -4

Put x = 0.
2B = A = -4
B = -2

Compare coefficient of x².
C = 3


2.
A(2x + 1)² - 3Bx + (B - C) ≡ (4x - 1)(x - 4)

Compare coefficient of x².
4A = 4
A = 1

Put x = 4.
81 - 12B + B - C = 0
11B + C = 81 ...[1]

Put x = 0.
1 + B - C = 4
B - C = 3 ...[2]

[1] + [2] gives
12B = 84
B = 7

C = B - 3 = 4

1.
(x+2)(Cx+B)=3x^2+4x+A
put x=-2
3(-2)^2 -8+A=0
A=-4
right=3x^2+4x-4
right=(3x-2)(x+2)
C=3
B=-2

2.
A(2x+1)^2-3Bx+(B-C)=(4x-1)(x-4)
left=4Ax^2+4Ax+A-3Bx+B-C
left=4Ax^2+(4A-3B)x+A+B-C
rigt=4x^2-17x+4
A=1
4-3B=-17
B=7
A+B-C=4
8-C=4
C=-4