最新数学初二基础知识点实数
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√3X-1=√2X
求X
{√5X-3√Y=1}
{√3X-√5Y=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
