Question

几道数学分式化简题（有图）

第七题，第十，十一十二题，急！！！！！

Answer 1

7.
(1)(a^2+4ab-5b^2)/(a-b)
=(a-b)(a+5b)/(a-b)
=a+5b
(2)(a^2-5a+6)/(a^2-7a+12)
=(a-2)(a-3)/(a-3)(a-4)
=(a-2)/(a-4)
10.
∵x-2y=0,∴x=2y.
(x^2-3xy+y^2)/(2x^2+xy-3y^2)
=(4y^2-6y^2+y^2)/(8y^2+2y^2-3y^2)
=(4-6+1)/(8+2-3)
=-1/7
11.
原式=a(a+b)/(a+b)(a-4b)
=a/(a-4b)
=0.5/(0.5-4*0.25)
=0.5/(-0.5)
=-1
12.
设x/2=y/3=z/4=k
则x=2k,y=3k,z=4k
原式=(2k*3k+3k*4k+4k*2k)/(4k^2+9k^2+16k^2)
=26k^2/29k^2
=26/29

Answer 2

同上，
10、=（x-y)(x-2y)/(x-y)(2x+3y)=(x-y)/(2x+3y)=0