初二數(shù)學上冊實數(shù)

初二數(shù)學上冊實數(shù) 實數(shù)包括有理數(shù)和無理數(shù)。其中無理數(shù)就是無限不循環(huán)小數(shù) , 有理數(shù)就包括整數(shù)和分數(shù)。小編整理了關(guān)于初二數(shù)學上冊實數(shù)的概念和實數(shù)的計算方法 , 以供同學們參詳和練 習 ! 1. 被開方數(shù)含有平方因數(shù)：分解因數(shù)( 準確找到平方因數(shù) ) 2. 被開方數(shù)含有分母：分母變成平方數(shù) 解方程 3 X-1=2 X 求 X {5 X-3 Y=1} {3 X-5 Y=2} 注： X 全部不在根號內(nèi) (1/2x)^2+10/9x^2 =[1/(4x^2)+10/(9x^2)] =49/36x^2 若 x0,=7/(6x) 若 x0,=-7/(6x) a^4mb^2n+1 =(a^2mb^n)^2+1 =a^2mb^n+1 (4a^5+8a^4)(a^2+3a+2) =[4a^4(a+2)][(a+2)(a+1)] 第 1 頁 =[4a^4(a+2)^2(a+1)] =2a^2(a+2)(a+1) . 3(1/6)-4(50)+30(2/3) 答案 3(1/6)-4(50)+30(2/3) = 36/6-452+306/3 =6/2-202+106 ①58 -232+50 =5*32-2*42+52 =2(15-8+5) =122 ②6-3/2-2/3 =6-6/2-6/3 =6/6 ③(45+27) -(4/3+125) =(35+33)-(23/3+55) =-25+75/3 ④(4a -50b)-2(b/2+9a) =(2a-52b)-2(2b/2+3a) =-4a-62b ⑤4x*(3x/2 -x/6) =2x(6x/2-6x/6) =2x*(6x/3) =2/3*x*6 ⑥(xy -yx)xy =xyxy-yxxy =x-y ⑦(37+23)(23 -37) =(23)^2-(37)^2 =12-63 =-51 ⑧(32 -33)(42+27) =(42-33)(42+33) =(42)^2-(33)^2 =32-27 =5 ⑨(36 -4)?? =(36)^2-2*36*4+(4)^2 =54-126+4 =58-126 ⑩(1+2 -3)(1-2+3) =[1+(2-3)][1-(2-3)] =1-(2-3)^2 =1-(2+3+26) =-4-26 1. =55 - 1/255 - 4/55 =5*(5-1/25-4/5) =24/55 2.=144+576 =720 =125 2.)(8/13)^2-(2/13)^2 = (8/13+2/13)(8/13-2/13) =(2/13)15 第 2 頁 3.3(1/6)-4(50)+30(2/3) 答案 3(1/6)-4(50)+30(2/3) = 36/6-452+306/3 =6/2-202+106 2. (1- 根號 2)/2 乘以 (1+ 根號 2)/2 題是這樣的二分之一減 根號 2 乘以二分之一加根號 2 答案： (1- 根號 2)/2 乘以 (1+ 根號 2)/2 =(1-2)*(1-2)/4 =(1-2)/4 =-1/4 3.(1/2x)^2+10/9x^2 [(1/2x)^2+10/9x^2] =(x^2/4+10x^2/9) =(9x^2/36+40x^2/36) =(49x^2/36) =7x/6; 4.a^4mb^2n+1(a 、b 為正數(shù) ) [(a^4mb^2n)]+1(a 、b 為正數(shù) ) =a^2mb^n+1; 5.(4a^5+8a^4)(a^2+3a+2)(a=0) [(4a^5+8a^4)(a^2+3a+2)](a=0) =[4a^4(a+2)(a+2)(a+1)] =[(2a^2)^2(a+2)^2(a+1)] =2a^2(a+2)(a+1). 第 3 頁