计算.(1)(5x-2y)2+20xy;(2)(x-3)2(x+3)2;(3)(3x-5)2-(2x+7)2;(4)(x+y+1)(x+y-1)
题型:解答题难度:一般来源:不详
计算. (1)(5x-2y)2+20xy; (2)(x-3)2(x+3)2; (3)(3x-5)2-(2x+7)2; (4)(x+y+1)(x+y-1) |
答案
(1)(5x-2y)2+20xy =25x2-20xy+4y2+20xy =25x2+4y2;
(2)(x-3)2(x+3)2 =(x2-9)2 =x4-18x2+81;
(3)(3x-5)2-(2x+7)2 =9x2-30x+25-(4x2+28x+49) =9x2-30x+25-4x2-28x-49 =5x2-58x-24;
(4)(x+y+1)(x+y-1) =[(x+y)+1][(x+y)-1] =(x+y)2-1 =x2+2xy+y2-1. |
举一反三
(-2m+3)(______)=4m2-9,(-2ab+3)2=______ |
计算. (1)89.82; (2)472-94×27+272. |
计算: (1)(2x+1)(-2x+1) (2)(2a-b2)2 (3)(3x+1)2(3x-1)2 (4)(x+1)(x2+1)(x4+1)(x-1) |
下列运用平方差公式计算,错误的是( )A.(x+1)(x-1)=x2-1 | B.(a+b)(a-b)=a2-b2 | C.(2x+1)(2x-1)=2x2-1 | D.(-a+b)(-a-b)=a2-b2 |
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下列运算中,正确的是( )A.(a-b)(a+b)=a2+b2 | B.(a-b)2=a2-b2 | C.(a+b)2=a2+ab+b2 | D.(m-1)2=m2-2m+1 |
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