高分求几道初二计算题,(2x+y)^2-(x+2y)^249(a-b)^2-16(a+b)^2(a-B)x^2+(b-a)Y^2
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高分求几道初二计算题,(2x+y)^2-(x+2y)^249(a-b)^2-16(a+b)^2(a-B)x^2+(b-a)Y^2
高分求几道初二计算题,
(2x+y)^2-(x+2y)^2
49(a-b)^2-16(a+b)^2
(a-B)x^2+(b-a)Y^2
高分求几道初二计算题,(2x+y)^2-(x+2y)^249(a-b)^2-16(a+b)^2(a-B)x^2+(b-a)Y^2
1.(2x+y)^2-(x+2y)^2 =(2x+y+x+2y)*[2x+y-(x+2y)]=(3x+3y)*(x-y) = 3x^2 - 3y^2
2.49(a-b)^2-16(a+b)^2 =[7(a-b)]^2 - [4(a+b)]^2 = [7a-7b + 4a+4b] * [7a-7b -(4a+4b)] =(11a-3b)*(3a-11b)= 33a^2 + 33b^2 -130ab
3.(a-b)x^2+(b-a)Y^2 = (a-b)x^2 - (a-b)Y^2 = (a-b)(x^2 - Y^2) 还可以进一步等于(a-b)(x-y)(x+y)
答案:
回答完毕,给分吧..
第一 3x^2 - 3y^2
第二 33a^2 + 33b^2 -130ab
第三 (a-b)(x-y)(x+y)
貌似跟LS的差不多哦
利用完全平方公式a^2-b^2=(a+b)(a-b)
(1)
(2x + y - x -2y)^2
=(x - y)^2
=x^2 -2xy + y^2
(2)
49(a-b)^2-16(a+b)^2
=〔7(a - b)〕^2 -〔4(a + b)〕^2
=(7a -7b - 4a- 4b)^2
=(3a- 3b)^2 =9a^2 -18ab + 9b^2
(3)
(a-b)x^2+(b-a)Y^2
=(a -b)x^2 -(a -b)Y^2
=(a-b)(x^2-Y^2)
=(a-b)(x+Y)(x-Y)