最新最新数学初二基础知识点实数.doc

最新数学初二基础知识点实数
第 2 页
最新数学初二基础知识点实数
　　：分解因数(准确找到平方因数)
：分母变成平方数
解方程3 X-1=2 X
求X
{5 X-3 Y=1}
{3 X-5 Y=2}
注：X全部不在根号内
(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)]
=[4a^4(a+2)^2(a+1)]
=2a^2(a+2)(a+1)
. 3(1/6)-4(50)+30(2/3)
第 4 页
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
(1/6)-4(50)+30