问题
解答题
计算 (1)(
(2)已知x+
(3)(x+6)2-(x-3)(x+3)2 (4)[(3xy+z)2-z2]÷xy. |
答案
(1)原式=1+9-
-91 3
=
;2 3
(2)∵x+
=10,1 x
∴(x+
)2=x2+2+1 x
=100,1 x2
则x2+
=98;1 x2
(3)原式=x2+12x+36-(x-3)(x2+6x+9)
=x2+12x+36-(x3-27)
=x2+12x+36-x3+27;
(4)原式=(9x2y2+6xyz+z2-z2)÷xy
=9xy+6z.