Question

几道简单的题、帮个忙呗、(a^2+1)-4a^2 12/(m^2-9)-2/m-3 若x/2=y/3=z/5 且3x+2

Answer 1

①(a^2+1)-4a^2 =1-3a^2

② 12/(m^2-9)-2/m-3

=12/(m+3)(m-3)-2/m-3

=12-2m-6/(m+3)(m-3)

=-2/(m+3)

③这是一种题型

解题模式就是令x/2=y/3=z/5=k

得x=2k

y=3k

z=5k

代入第二个式子得k=2

x=4

y=6

z=10