回答:
#v = 21#
説明:
#1 / v +(3v + 12)/(v ^ 2-5v)=(7v-56)/(v ^ 2-5v)#
#1 / v +(3v + 12)/(v ^ 2-5v) - (7v-56)/(v ^ 2-5v)= 0#
一般的な分母は #v ^ 2-5v = v(v-5)#
#(v-5 + 3v + 12-(7v-56))/(v ^ 2-5v)= 0#
#(v-5 + 3v + 12-7v + 56)/(v ^ 2-5v)= 0#
#(v + 3v-7v-5 + 12 + 56)/(v ^ 2-5v)= 0#
#( - 3v + 63)/(v ^ 2-5v)= 0#
#-3v + 63 = 0#
#-3v = -63#
#v =( - 63)/( - 3)#
#v = 21#