å·²ç¥xçå¹³æ¹å5xå2015çäºé¶ï¼æ±ä»£æ°å¼xå2çä¸æ¬¡æ¹åxå1çå¹³æ¹å 1åä¹xå2çå¼
解ï¼x^2-5x-2015=0
x²-5x=2015
x-2åä¹æ¬å·x-2æ¬å·ä¸æ¬¡æ¹åæ¬å·x-1æ¬å·äºæ¹å1
=[(x-2)³-(x-1)²-1]/(x-2)
=[(x-2)³-(x-1+1)(x-1-1)]/(x-2)
=[(x-2)³-x(x-2)]/ï¼x-2)
=[(x-2)(x²-4x+4-x)]/(x-2)
=x²-5x+4
=2015+4
=2019
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