九上二次根式练习题

3个回答

  • 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)²

    =(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