✔ 最佳答案
1. ( 2x - 1 )( x + 3 ) + 2x - 1 ≡ Ax² + Bx + C
2x² + 5x - 3 + 2x - 1 ≡ Ax² + Bx + C
2x² + 7x - 4 ≡ Ax² + Bx + C
∴ A = 2
B = 7
C = -4
2. A( 2x - 3 ) + B( 4x - 7 ) ≡ 1
2Ax - 3A + 4Bx - 7B ≡ 1
( 2A + 4B )x - ( 3A + 7B ) ≡ 1
∴ 2A + 4B = 0
3A + 7B = -1
∴ A = 2
B = -1
3. ( x + 1 )( x - 2 )( x + 3 ) ≡ x³ + Ax² + Bx + C
x³ + 2x² - 5x - 6 ≡ x³ + Ax² + Bx + C
∴ A = 2
B = -5
C = -6
4. A ( x + 2 )( x - 1 ) + B ( x - 1) ≡ 3x² + 5x - 8
A ( x² + x - 2 ) + B ( x - 1 ) ≡ 3x² + 5x - 8
Ax² + ( A + B )x - ( 2A + B ) ≡ 3x² + 5x - 8
∴ A = 3
A + B = 5
2A + B = 8
∴ A = 3
B = 2
5. A( x+2 )( x-1 ) + B( x+1 )( x-1 ) + C( x+2 )( x+1 ) ≡ 6x
A( x² + x - 2 ) + B( x² - 1 ) + C( x² + 3x + 2 ) ≡ 6x
( A + B + C )x² + ( A + 3C )x + ( 2C - 2A - B ) ≡ 6x
∴ A + B + C = 0
A + 3C = 6
2C - 2A - B = 0
∴ A = 3
B = -4
C = 1