If y=7, when x=6, how do you find y when x=-21 given that y varies inversely as x?

1 Answer
Mar 19, 2017

Answer:

#y=color(green)(-2)#

Explanation:

If #y# varies inversely as #x# then
#color(white)("XXX")x xx y=c# for some constant #c#

We are told that #(x,y)=(6,7)# is a solution to the required relation;
so
#color(white)("XXX")6 xx 7 =c color(white)("XX")rarrcolor(white)("XX")c=42#

#color(white)("XXXXXXXXXXX")rarrcolor(white)("XX")x xx y =42#

When #x=-21#
#color(white)("XXX")(-21) xx y = 42color(white)("XX")rarrcolor(white)("XX")y=-2##