已知x+2y=4,xy=1,则x3+8y3=______.
题型:填空题难度:一般来源:不详
已知x+2y=4,xy=1,则x3+8y3=______. |
答案
∵x+2y=4,xy=1, ∴x3+8y3 =(x+2y)(x2-2xy+4y2) =(x+2y)[(x+2y)2-6xy] =4×(16-6) =40. 故答案为:40. |
举一反三
已知2x+y=4,求代数式[(x+y)2-(x-y)2-2y(x-y)]÷4y的值. |
计算: (1)6a5b6c4÷(-3a2b3c)÷(2a3b3c3). (2)(x-4y)(2x+3y)-(x+2y)(x-y). (3)[(-2x2y)2]3•3xy4. (4)(m-n)(m+n)+(m+n)2-2m2. |
当x=-1,y=-2时,求代数式[2x2-(x+y)(x-y)][(-x-y)(-x+y)+2y2]的值. |
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