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初二數(shù)學(xué)上冊(cè)實(shí)數(shù)
實(shí)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?jǐn)?shù)。小編整理了關(guān)于初二數(shù)學(xué)上冊(cè)實(shí)數(shù)的概念和實(shí)數(shù)的計(jì)算方法 , 以供同學(xué)們參詳和練
習(xí) !
1. 被開方數(shù)含有平方因數(shù)：分解因數(shù)( 準(zhǔn)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(hào)內(nèi)
(1/2x)^2+10/9x^2
=[1/(4x^2)+10/(9x^2)]
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 -
3、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 =1
4、2-63 =-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/
5、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(hào) 2)/2 乘以 (1+ 根號(hào) 2)/2 題是這樣的二分之一減
根號(hào) 2 乘以二分之一加根號(hào) 2 答案： (1- 根號(hào) 2)/2 乘以 (1+
根號(hào) 2)/2 =(1-2)*(1-2)/4 =(1-2)/4 =-1/4 3.(1/2x)^2+10/9x^2 [(
6、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
初二數(shù)學(xué)上冊(cè)實(shí)數(shù)
