计算题:(1)99×101 (公式法)(2)(4x2y+5xy﹣7y)﹣(5x2y﹣4xy+x)(3)(x﹣2y)2+4(x﹣y)(x+y);(4)(a+...

2023-07-10 17:11发布

这道初中数学的题目是:
计算题:
(1)99×101 (公式法)
(2)(4x2y+5xy﹣7y)﹣(5x2y﹣4xy+x)
(3)(x﹣2y)2+4(x﹣y)(x+y);
(4)(a+2b﹣c)(a+2b+c)
(5)(2x3y4z2+4x3y3z3﹣6x2y3z5)÷(2x2yz2
(6)(x+3y)(x﹣2y)﹣x3÷x+6y2,其中x=2,y=﹣3
1条回答
btz1982
2023-07-10 17:25
这道初中数学题的正确答案为:
解:(1)原式=(100﹣1)(100+1),
=1002﹣1,
=10000﹣1,
=9999;
(2)(4x2y+5xy﹣7y)﹣(5x2y﹣4xy+x),
=4x2y+5xy﹣7y﹣5x2y+4xy﹣x,
=(4﹣5)x2y+(5+4)xy﹣7y﹣x,
=﹣x2y+9xy﹣7y﹣x;
(3)(x﹣2y)2+4(x﹣y)(x+y),
=x2﹣4xy+4y2+4x2﹣4y2
=5x2﹣4xy;
(4)设:a+2b=m,
则原式(a+2b﹣c)(a+2b+c)=(m﹣c)(m+c),
=m2﹣c2
∵a+2b=m,
∴m2﹣c2=(a+2b)2﹣c2
=a2+4ab+4b2﹣c2
(5)(2x3y4z2+4x3y3z3﹣6x2y3z5)÷(2x2yz2),
=2x3y4z2÷2x2yz2+4x3y3z3÷2x2yz2﹣6x2y3z5÷2x2yz2
=xy3+2xy2z﹣3y2z3
(6)(x+3y)(x﹣2y)﹣x3÷x+6y2
=x2+xy﹣6y2﹣x2+6y2
=xy,
当x=2,y=﹣3时,原式=2×(﹣3)=﹣6
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