计算下列各式,然后回答问题.(a+4)(a+3)=______;(a+4)(a-3)=______;(a-4)(a+3)=______;(a-4)(a-3)=_
题型:填空题难度:一般来源:不详
计算下列各式,然后回答问题. (a+4)(a+3)=______;(a+4)(a-3)=______; (a-4)(a+3)=______;(a-4)(a-3)=______. (1)从上面的计算中总结规律,写出下式结果. (x+a)(x+b)=______. (2)运用上述结果,写出下列各题结果. ①(x+2008)(x-1000)=______; ②(x-2005)(x-2000)=______. |
答案
(a+4)(a+3)=a2+7a+12; (a+4)(a-3)=a2+a-12; (a-4)(a+3)=a2-a-12; (a-4)(a-3)=a2-7a+12. (1)(x+a)(x+b)=x2+(a+b)x+ab. (2)①(x+2008)(x-1000)=x2+1008x-2 008 000; ②(x-2005)(x-2000)=x2-4 005x+4 010 000. |
举一反三
若(x-2)(x+m)=x2+nx-6,则m=______n=______. |
下列式子正确的是( )A.(a+2)(a-2)=a2-2 | B.(a-b)2=a2-b2 | C.(x+2)(x-3)=x2-5x-6 | D.(m-n)(n+m)=m2-n2 |
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设(2x+m)(x-5)的积中不含x项,则m等于( ) |
下列运算结果错误的是( )A.(x+y)(x-y)=x2-y2 | B.(a-b)2=a2-b2 | C.(x+y)(x-y)(x2+y2)=x4-y4 | D.(x+2)(x-3)=x2-x-6 |
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