初一下数学题 那位好心人帮帮忙(1)(2x+y+1)(2x+y-1) (2)(x-2)(x+2)-(x+1)(x-3) (3)(ab+1)²-(ab-1)² (4) (2x-y)²-4(x-y)(x+2y)利用完全平方公式计算(1)63² (2)998²
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![初一下数学题 那位好心人帮帮忙(1)(2x+y+1)(2x+y-1) (2)(x-2)(x+2)-(x+1)(x-3) (3)(ab+1)²-(ab-1)² (4) (2x-y)²-4(x-y)(x+2y)利用完全平方公式计算(1)63² (2)998²](/uploads/image/z/2613135-39-5.jpg?t=%E5%88%9D%E4%B8%80%E4%B8%8B%E6%95%B0%E5%AD%A6%E9%A2%98+%E9%82%A3%E4%BD%8D%E5%A5%BD%E5%BF%83%E4%BA%BA%E5%B8%AE%E5%B8%AE%E5%BF%99%EF%BC%881%EF%BC%89%EF%BC%882x%2By%2B1%EF%BC%89%EF%BC%882x%2By-1%EF%BC%89++%EF%BC%882%EF%BC%89%EF%BC%88x-2%29%28x%2B2%29-%28x%2B1%29%28x-3%29+++++%283%29%28ab%2B1%29%26sup2%3B-%28ab-1%29%26sup2%3B+%284%29++%282x-y%29%26sup2%3B-4%28x-y%29%28x%2B2y%29%E5%88%A9%E7%94%A8%E5%AE%8C%E5%85%A8%E5%B9%B3%E6%96%B9%E5%85%AC%E5%BC%8F%E8%AE%A1%E7%AE%97%EF%BC%881%EF%BC%8963%26sup2%3B++++%EF%BC%882%EF%BC%89998%26sup2%3B)
初一下数学题 那位好心人帮帮忙(1)(2x+y+1)(2x+y-1) (2)(x-2)(x+2)-(x+1)(x-3) (3)(ab+1)²-(ab-1)² (4) (2x-y)²-4(x-y)(x+2y)利用完全平方公式计算(1)63² (2)998²
初一下数学题 那位好心人帮帮忙
(1)(2x+y+1)(2x+y-1) (2)(x-2)(x+2)-(x+1)(x-3) (3)(ab+1)²-(ab-1)²
(4) (2x-y)²-4(x-y)(x+2y)
利用完全平方公式计算
(1)63² (2)998²
初一下数学题 那位好心人帮帮忙(1)(2x+y+1)(2x+y-1) (2)(x-2)(x+2)-(x+1)(x-3) (3)(ab+1)²-(ab-1)² (4) (2x-y)²-4(x-y)(x+2y)利用完全平方公式计算(1)63² (2)998²
1(2x+y+1)(2x+y-1)
= (2x+y)^2-1^2
=4x^2+y^2+4xy-1
(2)(x-2)(x+2)-(x+1)(x-3)
=(x^2-2^2)-(x^2-3x+x-3)
=x^2-4-x^2+2x+3
(3)(ab+1)²-(ab-1)²
=a^4 b^4-1
(4) (2x-y)²-4(x-y)(x+2y)
=(4X^2+y^2-4xy)-(4x^2+4xy-y^2)
=2y^2-8xy
利用完全平方公式计算
(1)63²
=(60+3)^2
=60^2+3^2+2*60*3
=3600+9++360
=3969
(2)998²
=(1000-2)^2
=1000²-2*1000*2+2²
=1000000-4000+4
=996004
(1)(2x+y+1)(2x+y-1)=(2x+y)² -1
(2)(x-2)(x+2)-(x+1)(x-3)=x²-4-(x-1)²+4
(3)(ab+1)²-(ab-1)²=(ab-1)×(ab+1)
(4) (2x-y)²-4(x-y)(x+2y)=(2x-y)²-4(xy-y²)(x&...
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(1)(2x+y+1)(2x+y-1)=(2x+y)² -1
(2)(x-2)(x+2)-(x+1)(x-3)=x²-4-(x-1)²+4
(3)(ab+1)²-(ab-1)²=(ab-1)×(ab+1)
(4) (2x-y)²-4(x-y)(x+2y)=(2x-y)²-4(xy-y²)(x²-y²)
(1)63² =(60+3)²
(2)998²=(1000-2)²
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(1)原式=(2x+y)²-1²
(2)原式=x²-4-(x²-2x-3)
=x²-4-x²+2x+3
=2x-1
(3)原式=(ab+1+ab-1)(ab+1-ab+1)
=2ab*2
...
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(1)原式=(2x+y)²-1²
(2)原式=x²-4-(x²-2x-3)
=x²-4-x²+2x+3
=2x-1
(3)原式=(ab+1+ab-1)(ab+1-ab+1)
=2ab*2
=4ab
(4)原式=4x²-4xy+y²-(4x-4y)(x+2y)
=4x²-4xy+y²-(4x²+4xy+8y²)
=4x²-4xy+y²-4x²-4xy-8y²
=-8xy-7y²
(1)63²
=(60+3)²
=60²+2*60*3+3²
=3600+360+9
=3969
(2)998²
=(1000-2)²
=1000²-2*1000*2+2²
=1000000-4000+4
=996004
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我也求完全平方差的公式
1 (2x+y)(2x+y)—1 等于4x平方+4xy+y平方—1
2 x平方—4—x+4 等于0
3 (ab+1—ab+1)(ab+1+ab—1) 等于 (ab)的平方
4 4x的平方—4xy+y的平方—4x平方—4xy+8y平方 等于 9y平方—8xy
(64—1)的平方 64平方—64X2+1 等于 2的12次方...
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1 (2x+y)(2x+y)—1 等于4x平方+4xy+y平方—1
2 x平方—4—x+4 等于0
3 (ab+1—ab+1)(ab+1+ab—1) 等于 (ab)的平方
4 4x的平方—4xy+y的平方—4x平方—4xy+8y平方 等于 9y平方—8xy
(64—1)的平方 64平方—64X2+1 等于 2的12次方—2的7次方+1 等于 3969
(1000—2)的平方 996004
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