數學專家請快進!!!－zogfly3的部落格

標題:

數學專家請快進!!!

發問:

求解答以下難題!!!必須要有步驟!!!plz!!!thz!!! 1)(x+y+z)(x+y-z) 2)16p^2+48pq+36q^2 3)6xy+18xz / 8yz+24z^2 4)x / x^2+2x - 1 / x-2 5)解 2a+b=4 { a-2b=7 急!!!快!!!

最佳解答:

1)(x+y+z)(x+y-z) =x(x+y-z)+y(x+y-z)+z(x+y-z) =x^2+xy-xz+xy+y^2-yz+xz+yz-z^2 =x^2+2xy+y^2-z^2 2)16p^2+48pq+36q^2 =4(4p^2+12pq+9q^2) =4((2p)^2+2(2p)(3q)+(3q)^2) =4(2p+3q)^2 3)6xy+18xz/8yz+24z^2 =6x(y+3z)/8z(y+3z) =6x/8z =3x/4z 4)x/x^2+2x-1/x-2 =x/x(x+2)-1/x-2 =1/(x+2)-1/(x-2) =(x-2)-(x+2)/(x+2)(x-2) =-4/(x+2)(x-2) 5.2a+b=4------(1) a-2b=7------(2) (2)*2, 2a-4b=14------(3) (1)-(3), (2a+b)-(2a-4b)=4-14 5b=-10 b=-2 sub b=-2 into (2) a-2(-2)=7 a+4=7 a=3 therefore a=3,b=-2

其他解答:

1） X（X＋Y﹣Z）＋Y（X＋Y﹣Z）＋Z（X＋Y﹣Z）自已乘埋入去 2） (4P)^2+2(4)(6)+(6Q)^2 =(4P+6Q)^2 3 6X(Y＋3Z）／8Z（Y＋3Z）＝3X／4Z 4.X/x(x+2) - 1/x-2 = /x(x^2-4) =-4x/x(x^2-4) 5 a=7+2b 2(7+2b)+b=4 b=-2 when b=-2 a=3