计算:(1)(x+y-z)(x+y+z).(2)(x+y-z)(x-y-z).(3)(x+y+z)(x-y-z).(4)(x+y-z)(x-y+z).
题型:解答题难度:一般来源:不详
计算: (1)(x+y-z)(x+y+z). (2)(x+y-z)(x-y-z). (3)(x+y+z)(x-y-z). (4)(x+y-z)(x-y+z). |
答案
(1)原式=[(x+y)-z][(x+y)+z] =(x+y)2-z2 =x2+2xy+y2-z2;
(2)原式=[(x-z)+y][(x-z)-y] =(x-z)2-y2 =x2-2xz+z2-y2;
(3)原式=[x+(y+z)][x-(y+z)] =x2-(y+z)2 =x2-y2-z2-2yz;
(4)原式=[x+(y-z)][x-(y-z)] =x2-(y-z)2 =x2-y2-z2+2yz. |
举一反三
若81-xk=(x2+9)(x+3)(3-x),则k的值为( ) |
下列计算中,正确的是( )A.a2+a2=2a4 | B.(a-b)2=a2-b2 | C.(a+b)(b-a)=b2-a2 | D.(a+b)(a-2b)=a2-2b2 |
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(a-2b)2=______,(x-2)(x+2)=______. |
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