数学题十三道 求教 不要凑经验的.(1) (-2a+5)(-2a+3)(2) (3b+a)(a-3b)(3) 503*497(4) (-4a-b)(-4a+b)(5) [(-1/2)a-b^2][(1/2)a-b^2](6) [(2/3)x-7y][7y+(2/3)x](7) [3m-(1/4)]^2(8) 99.8^2(9) (5m+n^2)^2(10) 先化简再求值:(x-2)(x+2)-(4x+1)(x-2
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数学题十三道 求教 不要凑经验的.(1) (-2a+5)(-2a+3)(2) (3b+a)(a-3b)(3) 503*497(4) (-4a-b)(-4a+b)(5) [(-1/2)a-b^2][(1/2)a-b^2](6) [(2/3)x-7y][7y+(2/3)x](7) [3m-(1/4)]^2(8) 99.8^2(9) (5m+n^2)^2(10) 先化简再求值:(x-2)(x+2)-(4x+1)(x-2
数学题十三道 求教 不要凑经验的.
(1) (-2a+5)(-2a+3)
(2) (3b+a)(a-3b)
(3) 503*497
(4) (-4a-b)(-4a+b)
(5) [(-1/2)a-b^2][(1/2)a-b^2]
(6) [(2/3)x-7y][7y+(2/3)x]
(7) [3m-(1/4)]^2
(8) 99.8^2
(9) (5m+n^2)^2
(10) 先化简再求值:(x-2)(x+2)-(4x+1)(x-2)-x(x-3),其中x=-3
(11) 先化简再求值:x^2(x-2y)-(y-x^2)(-y-x^2),其中x=2,y=-1
(12) 若(a+1)^2+(1/2)|b-2|+(5+c)^2=0,求a^2014-b^3*c的值
(13) 已知:x^2-5x=14,求(x-1)(2x-1)-(x+1)^2+1的值
数学题十三道 求教 不要凑经验的.(1) (-2a+5)(-2a+3)(2) (3b+a)(a-3b)(3) 503*497(4) (-4a-b)(-4a+b)(5) [(-1/2)a-b^2][(1/2)a-b^2](6) [(2/3)x-7y][7y+(2/3)x](7) [3m-(1/4)]^2(8) 99.8^2(9) (5m+n^2)^2(10) 先化简再求值:(x-2)(x+2)-(4x+1)(x-2
(1)(2a-5)(2a-3)=4a²-16a+15 (2)-(3b+a)(3b-a)=a²-9b²(3)(500+3)(500-3)=250000-9(4)(4a+b)(4q-b)=8a²-b²(5)((1/2)a+b²)((1/2)a-b²)=1/4a²-b^4(6)提取前面一个括号的负号最后等于-49y²-4/9x²(7)9m²-3/2m+1/16 (8)(100-0.2)²=10000-4-0.04(9)25m²+10n²+n^4(10)x²-4-(4x²-7x-2)+x²+3(11)x²(x-2y)+y²-x^4(12)不(13)x²-5x-14=0,(x-7)(x+2)=0,所以x=7或x=-2 然后你自己代入那个算式