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青少版新概念3B 24
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你可能喜欢在4A+3B2=2A2B3的反应中,27gA与24gB2恰好完全反应,则物质A与A2B3的相对分子质量之比是( )A.9:34_百度知道谁能帮我讲一下这些因式分解的题1:x^2-9(x+y)^22:64(a-b)^2-49(a+b)^23:4(3a+2b)^2-(2a+3b)^24:X^4-16y^4我不太明白这些~
平方差公式:a^2-b^2=(a+b)(a-b)可以把右边展开来证明,即(a+b)(a-b)=a^2-ab+ab-b^2=a^2-b^2你这几道题都是用这个公式来做:1.x^2-9(x+y)^2=x^2-[3(x+y)]^2=[x+3(x+y)][x-3(x+y)]=(4x+3y)(-2x-3y)=-(2x+3y)(4x+3y)2.64(a-b)^2-49(a+b)^2=[8(a-b)]^2-[7(a+b)]^2=(8a-8b+7a+7b)(8a-8b-7a-7b)=(15a-b)(a-15b)3.4(3a+2b)^2-(2a+3b)^2 =[2(3a+2b)]^2-(2a+3b)^2=(6a+4b+2a+3b)(6a+4b-2a-3b)=(8a+7b)(4a+b)4.x^4-16y^4=(x^2)^2-(4y^2)^2=(x^2+4y^2)(x^2-4y^2)=(x^2+4y^2)[x^2-(2y)^2]==(x^2+4y^2)(x+2y)(x-2y)
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全是平方差啊,你用平方差公式就是了
都是两个平方相减 第一个 (X-3(X+Y))(X+3(X+Y))下面的你就都会了吧
自己看书,先化简,再配平
都是用 平方差公式: a^2-b^2=(a+b)(a-b)1: x^2-9(x+y)^2= x^2-(3x+3y)^2=(x+3x+3y)(x-(3x+3y))=(4x+3y)(-3y-2x)=-(4x+3y)(3y+2x)2: 64(a-b)^2-49(a+b)^2 =(8a-8b)^2-(7a+7b)^2 =(8a...
好像有个软件就是专门用来分解因式的,你去网上搜搜看
主要是应用平方差公式a^2-b^2=(a+b)(a-b)x^2-9(x+y)^2=x^2-(3x+3y)^2 =(x+3x+3y)(x-3x-3y)=-(4x+3y)(2x+3y)64(a-b)^2-49(a+b)^2=(8a-8b)^2-(7a+7b)^2=(8a-8b-7a-7b)(8a-8b+7a+7b)=(a-15b)(15a-b...
1. x^2-9(x+y)^2=x^2-(3x+3y)^2=[x+(3x+3y)]*[x-(3x+3y)]=(4x+3y)*(-2x-3y)=-8x^2-12xy-6xy-9y^2=-8x^2-18xy-9y^22.64(a-b)^2-49(a+b)^2=(8a-8b)^2-(7a+7b)^2=[(...
1.x^2-9(x+y)^2 =x^2-[3(x+y)]^2 =[x+3(x+y)][x-3(x+y)] =(4x+3y)(-2x-3y) =-(2x+3y)(4x+3y) 2.64(a-b)^2-49(a+b)^2 =[8(a-b)]^2-[7(a+b)]^2 =(8a-8b+7a+7b)(8a-8b-7a-7b) ...
1.x^2-9(x+y)^2=x^2-[3(x+y)]^2=[x+3(x+y)][x-3(x+y)]=(4x+3y)(-2x-3y)=-(2x+3y)(4x+3y)2.64(a-b)^2-49(a+b)^2=[8(a-b)]^2-[7(a+b)]^2=(8a-8b+7a+7b)(8a-8b-7a-7b)=(15a-b)...
1: x^2-9(x+y)^2=x^2-[3(x+y)]^2=[x+3(x+y)][x-3(x+y)]=(4x+3y)(-2x-3y)=-(4x+3y)(2x+3y); 2: 64(a-b)^2-49(a+b)^2 =[8(a-b)]^2-[7(a+b)]^2=[8(a-b)+7(a+b)][8(a-b)-7(a+b)]