第一题 9倍根号a-2倍根号a方x-3倍根号a分之b方-6倍根号9分之b方x 已知(b小于0)

2个回答

  • 1.

    9√a-2√(a^2x)-3√(b^2/a)-6√[(b^2x)/9]

    =9√a-2√(a^2x)+3b√(1/a)+6b√(x/9)

    =9√a-2√(a^2x)+3b√a+6b√(x/9)

    =9√a-2√(a^2x)+3b√a+2b√x

    =9√a-2a√x+3b√a+2b√x

    =9√a+3b√a+2b√x-2a√x

    =3√a(3+b)+2√x(b-a)

    2.

    a^2b-ab^2

    =ab(a-b)

    =(3+2√2)(3-2√2)[(3+2√2)-(3-2√2)]

    =[(3+2√2)-(3-2√2)]

    =3+2√2-3+2√2

    =4√2

    3.

    √x+√y=√5-√3

    √(xy)=√15-√3

    x+y=(√x+√y)^2-2√(xy)

    =(√5-√3)^2-2(√15-√3)

    =(3+5-2√15)-2√15+2√3

    =8-2√15-2√15+2√3

    =8-4√15+2√3

    4.

    x=(2+√3)/(2-√3)

    =(2+√3)^2/(2-√3)(2+√3)

    =(2+√3)^2

    =7+4√3

    y=(2-√3)/(2+√3)

    =(2-√3)^2/(2-√3)(2+√3)

    =(2-√3)^2

    =7+4√3

    x-y=7+4√3-7+4√3=8√3

    xy=(2-√3)/(2+√3)*(2+√3)/(2-√3)=1

    2x^2-3xy+2y^2

    =2x^2-4xy+2y^2+xy

    =2(x^2-2xy+y^2)+xy

    =2(x-y)^2+xy

    =2(x-y)^2+1

    =2*(8√3)^2+1

    =2*192+1

    =384+1

    =385