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CAÙC DAÏNG BAØI TAÄP CAÀN KHAI THAÙC
A) . DAÏNG 1: Phaân tích ña thöùc thaønh nhaân töû baèng phöông phaùp ñaët nhaân töû chung:
+ Baøi taäp :
1) Phaân tích caùc ña thöùc sau thaønh nhaân töû
a) 3x – 3y
b) 2x2 + 5x3 + x2y
c) 14x2y – 21 xy2 + 28x2y2
d) x(y – 1 ) – y(y – 1)
e) 10x(x – y) – 8y(y – x)
Giaûi:
a) 3x – 3y = 3(x – y)
b) 2x2 + 5x3 + x2y = x2(2 + 5x + y)
c) 14x2y – 21 xy2 + 28x2y2 = 7xy( 2x – 3y + 4xy)
d) x(y – 1 ) – y(y – 1) = (y – 1)(x – y)
e) 10x(x – y) – 8y(y – x) = 10x(x – y) + 8y(x – y) = 2 (x – y)(5x + 4y)
2) Tìm x , bieát :
a) 5x(x – 2000) – x + 2000 = 0
b) 5x2 = 13x
Giaûi: