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初二数学上册实数

[04-24 20:28:54]   来源:http://www.i3xuexi.com  初二数学学习指导   阅读:9506

[导读] )(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)答案3√(1/6)-4√(50)+30√(2/3)= 3×√6/6-4×5√2+30×√6/3=√6/2-20√2+10√6①5√8-2√32+√50 =5*3√2-2*4√2+5√2 =√2(15-8+5) =12√2②√6-√3/2-√2/3 =√6-√6/2-√6/3 =√6/6③(√45+√27)-(√4/3+√125) =(3√5+3√3)-(2√3/3+5√5) =-2√5+7&radi

初二数学上册实数,http://www.i3xuexi.com

  实数包括有理数和无理数。其中无理数就是无限不循环小数,有理数就包括整数和分数。小编整理了关于初二数学上册实数的概念和实数的计算方法,以供同学们参详和练习!

  1.被开方数含有平方因数:分解因数(准确找到平方因数)

  2.被开方数含有分母: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x>0,=7/(6x)

  若x<0,=-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)

  答案3√(1/6)-4√(50)+30√(2/3)

  = 3×√6/6-4×5√2+30×√6/3

  =√6/2-20√2+10√6

  ①5√8-2√32+√50 =5*3√2-2*4√2+5√2 =√2(15-8+5) =12√2

  ②√6-√3/2-√2/3 =√6-√6/2-√6/3 =√6/6

  ③(√45+√27)-(√4/3+√125) =(3√5+3√3)-(2√3/3+5√5) =-2√5+7√5/3

  ④(√4a-√50b)-2(√b/2+√9a) =(2√a-5√2b)-2(√2b/2+3√a) =-4√a-6√2b

  ⑤√4x*(√3x/2-√x/6) =2√x(√6x/2-√6x/6) =2√x*(√6x/3) =2/3*x*√6

  ⑥(x√y-y√x)÷√xy =x√y÷√xy-y√x÷√xy =√x-√y

  ⑦(3√7+2√3)(2√3-3√7) =(2√3)^2-(3√7)^2 =12-63 =-51

  ⑧(√32-3√3)(4√2+√27) =(4√2-3√3)(4√2+3√3) =(4√2)^2-(3√3)^2 =32-27 =5

  ⑨(3√6-√4)?? =(3√6)^2-2*3√6*√4+(√4)^2 =54-12√6+4 =58-12√6

  ⑩(1+√2-√3)(1-√2+√3) =[1+(√2-√3)][1-(√2-√3)] =1-(√2-√3)^2 =1-(2+3+2√6) =-4-2√6

  1. =5√5 - 1/25√5 - 4/5√5 =√5*(5-1/25-4/5) =24/5√5 2.=√144+576 =√720 =12√5

  2.)√(8/13)^2-(2/13)^2 = √(8/13+2/13)(8/13-2/13) =(2/13)√15

  3.3√(1/6)-4√(50)+30√(2/3) 答案3√(1/6)-4√(50)+30√(2/3) = 3×√6/6-4×5√2+30×√6/3 =√6/2-20√2+10√6

  2. (1-根号2)/2乘以(1+根号2)/2 题是这样的二分之一减根号2乘以二分之一加根号2 答案:(1-根号2)/2乘以(1+根号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为正数) [√(a^4mb^2n)]+1(a、b为正数) =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).


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