If y varies inversely as x, and y = 1 as x = -2, how do you find y for the x-value of -1?

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Answer 1 · 2016-06-16T17:57:52

#y=2.#

Given that #yprop1/x.#
#:. y=k/x,#, or, #xy=k# ...(1), where #k!=0# is constant of variation.

To determine #k,# we use the given cond. that, #x=-2rArry=1.#

By (1) then, #k=-2.# Hence (1) #rArr xy=-2.#...(2)

Now, when #x=-1, y=?#

(2) #rArr (-1)y=-2,# or #y=2.#

Answer 2 · 2016-06-16T18:00:39

#y =2#

This is an example of inverse proportion, or inverse variation.

To change a proportion into an equation, multiply by a constant and then use the values given to find the value of the constant.

#y = k/x rArr k = xy#

#k= -2 xx 1 = -2#

So, # y = (-2)/x#

When #x = -1, " " y = (-2)/(-1)#