已知:x2-3x=1,求下列各式的值.
(1)
(2)x4-6x3+10x2-3x+6.
网友回答
解:(1)∵x2-3x=1,
∴x1=,x2=,
∴当x1=时,=+=11;
当x2=时,=+=11;
(2)∵x2-3x=1,
∴x4-6x3+10x2-3x+6
=x4-6x3+9x2+x2-3x+6
=x4-6x3+9x2+7
=x2(x2-6x+9)+7
=x2(1-3x+9)+7
=x2-3x3+9x2+7
=-3x3+10x2+7
=-x(x2-3x+x2-3x+x2-3x-x)+7
=-x(3-x)+7
=x2-3x+7=1+7=8;
解析分析:(1)先根据x2-3x=1,求出x的值,再代入进行计算即可;
(2)先把要求的式子进行因式分解,再把x2-3x=1即可求出