急需解决三道七年级因式分解数学题,哪位可以帮帮忙!!!
\u6025\u9700\u89e3\u51b3\u56db\u9053\u4e03\u5e74\u7ea7\u56e0\u5f0f\u5206\u89e3\u6570\u5b66\u9898,\u54ea\u4f4d\u53ef\u4ee5\u5e2e\u5e2e\u5fd9!!!(1-x^2)(1-y^2)+4xy
=1-x^2-y^2+x^2y^2+4xy
=(x^2y^2+2xy+1)-(x^2-2xy+y^2)
=(xy+1)^2-(x-y)^2
=(xy+x-y+1)(xy-x+y+1)
x^2-x-2y-4y^2
=(x^2-4y^2)-x-2y
=(x+2y)(x-2y)-(x+2y)
=(x+2y)(x-2y-1)
4x^2-4xy+y^2-44x+22y+40
=(2x-y)^2-22(2x-y)+121-81
=(2x-y-11)^2-9^2
=(2x-y-11+9)(2x-y-11-9)
=(2x-y-2)(2x-y-20)
x^3y^2-5x^2y^2-24xy^2
=xy^2(x^2-5x-24)
=xy^2(x-8)(x+3)
1. \u5341\u5b57\u4ea4\u53c9\u6cd5 ... \u539f\u65b9\u53ef\u5316\u4e3a \uff1a\u3016\uff08X\u7684\u5e73\u65b9+X\uff09-2\u3017*\u3016\uff08X\u7684\u5e73\u65b9+X\uff09-6\u3017
2.\u4f60\u5199\u7684\u597d\u4e71...
3.\u7b80\u5355 \u5148\u628a \u540e\u9762\u7684X+Y=2\u5e73\u65b9 \u53ef\u5f97 \uff1aX\u4e8c\u6b21\u65b9+y\u7684\u4e8c\u6b21\u65b9+2XY=4 \u53c8\u56e0\u4e3ax\u7684\u4e8c\u6b21\u65b9+y\u7684\u4e8c\u6b21\u65b9=3 \u6240\u4ee5..2XY=1 XY=1/2
a^2+14ab+45b^2 = (a+5b)*(a+9b)
a^2-9ab+20b^2 = (a-5b)*(a-4b)
2:十字相乘法+平方差公式
a^4-5a^2+4 =(a^2-1)*(a^2-4）=（a+1)*（a-1)*(a+2)*(a-2)
3:提公因式法+十字相乘法
2a+4+3ab+6b = 2(a+2)+3b(a+2) = (a+2)*(2+3b)
建议你加强十字相乘法的训练 这个方法很常用
⑹十字相乘法
这种方法有两种情况。
①x^2+(p+q)x+pq型的式子的因式分解
这类二次三项式的特点是：二次项的系数是1；常数项是两个数的积；一次项系数是常数项的两个因数的和。因此，可以直接将某些二次项的系数是1的二次三项式因式分解：x^2+(p+q)x+pq=(x+p)(x+q) ．
②kx^2+mx+n型的式子的因式分解
如果如果有k=ac，n=bd，且有ad+bc=m时，那么kx^2+mx+n=(ax+b)(cx+d)．
图示如下：
·a b
· ×
·c d
例如：因为
·1 -3
· ×
·7 2
且2-21=-19，
所以7x^2-19x-6=(7x+2)(x-3)．
1.(1) (a+5b)(a+9b) (2)(a-4b)(a-5b)
2. (a-1)(a+1)(a-2)(a+2)
3. (a+2)(3b+2)
1.分解因式:(1)a的二次方+14ab+45b的二次方(2)a的二次方-9ab+20b的二次方
(a+5b)(a+9b)
(a-4b)(a-5b)
2.分解因式:a的四次方-5a的二次方+4
(a+2)(a-2)(a+1)(a-1)
3.分解因式:2a+4+3ab+6b
(a+2)(3b+2)
绛旓細(x-2)锛坸-q)=x鐨勫钩鏂+(-2-q)x+2q =x鐨勫钩鏂+px+8 鎵浠-2-q=p 2q=8 鎵浠=4 p=-2-q=-6
绛旓細棰1锛144锛坅+2b锛塣2-169(2a-b)^2 =[12(a+2b)+13(2a-b)][12(a+2b)-13(2a-b)]=(38a+11b)(-14a+37b)=-(38a+11b)(14a-37b)棰2锛氾紙x^2-2x锛塣2+2(x^2-2x)+1 =(x²-2x+1)²=(x-1)^4
绛旓細1. a^2+2b^2+c^2-2b(a+c) = 0 => a^2+2b^2+c^2-2ab-2bc = 0 => a^2-2ab+b^2+b^2-2bc+c^2 = 0 => (a-b)^2+(b-c)^2 = 0 => a-b = 0; b-c = 0;=> a=b=c => 绛夎竟涓夎褰 2. 璁句腑闂撮偅涓鏁颁负x锛屽垯杩3涓繛缁鏁颁负x-2,x,x+2 (x-2)^2...
绛旓細1. (2a+b)^2-10(2a+b)+25 瑙ｏ細鍘熷紡=(2a+b-5)^2 锛堣繖閲屾槸灏2a+b鐪嬫垚鏄竴涓暣浣(鈯檕鈯)鍝︼級2. xy^2-8xy+16x 瑙ｏ細鍘熷紡=x(y^2-8y+16)=x(y-4)^2 3. 2x^2+2x+浜屽垎涔嬩竴 瑙ｏ細鍘熷紡=2锛坸^2+x+1/4)=2(x+1/2)^2 4. (x^2+9)^2-36x^2 瑙ｏ細...
绛旓細1.(X-1)2-Y2/X+Y-1 =(X+Y-1)(X-Y-1)/(X+Y-1) =X-Y-1 2.(X2-1)2/(X+1)2 =(X+1)2(X-1)2/(X+1)2 =(X+1)2 3.(a2-4)(a2+4)/a-2 =(a+2)(a-2)(a2+4)/(a-2) =(a2+4)(a+2) 瀛楁瘝鏃佺殑鏄簩娆℃柟銆傚笇鏈涜兘甯姪浣犮傝繖浜涗笉...
绛旓細鍥炵瓟锛氭病鏈 .....
绛旓細1.m鐨勫钩鏂瑰噺n鐨勫钩鏂癸紳锛坢锛媙锛壝楋紙m鈥攏锛夛紳9 鍒嗘儏鍐佃璁猴細1锛塵锛媙锛3 m锛峮锛3 m锛3锛宯锛0锛堣垗鍘伙級2锛塵锛媙锛濓紞9 m锛峮锛濓紞1 m锛濓紞5 n锛濓紞4 2.鎻愬彇鍏鍥犲紡xy鐨勫洓娆℃柟寰楀埌xy鐨勫洓娆℃柟涔樹互锛坸锛媦 )=1鐨勫洓娆℃柟脳4锛4 3.鎻愬彇鍏洜寮弜(2-a)鍗冲緱x(2-a)(1-x)4.锛堜竷鍒嗕箣浜寉...
绛旓細7.A 8.A 9.C 10.B
绛旓細锛7a-8b)^2-4x^2 =(7a-8b+2x)(7a-8b-2x)X^2(x-4)+y^2(4-x)=(x^2-y^2)(x-4)=(x+y)(x-y)(x-4)a^4-81 =(a^2+9)(a^2-9)=(a^2+9)(a+3)(a-3)11(a-b)+11/1(b-a)^3 =11(a-b)[1-121/1(b-a)^2]=11(a-b)[1+11/1(b-a)][1-11/1(b-...
绛旓細(x2-7x+6)(x2-x-6)+56 =(x-6)(x-1)(x-3)(x+2)+56 =[(x-6)(x+2)][(x-1)(x-3)]+56 =(x^2-4x-12)(x^2-4x+3)+56 =(x^2-4x)^2-9(x^2-4x)-36+56 =(x^2-4x)^2-9(x^2-4x)+20 =(x^2-4x-4)(x^2-4x-5)=(x^2-4x-4)(x-5)(x+1)=(x...
