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If y varies directly with x, and If y = -16 when x = 4, how do you find x when y = 20?

Answer 1

Eva Adamson

When #y =20# , #x# is #color(Blue)(-5#

#y# varies directly with #x# this implies #y# is directly proportional to #x#: #color(blue)(y prop x#

Upon introducing constant #k# (constant of proportionality ): #y = color(green)(k) x#........#(1)#

As per given data: when #y=-16, x=4#, substituting the above values in #(1)# to find #color(green)(k#

#-16 = k xx 4#

# k = -16/ 4#

# color(green)(k = -4#,

Finding #x# when #color(blue)(y =20# :

#y=kx#

#color(blue)(20) = color(green)(-4) xx x#

# x = 20/ (-4)#

#color(blue)(x= -5#

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Answer 2

Isaiah Anthony

To find x when y = 20, given that y varies directly with x and y = -16 when x = 4, you can use the direct variation formula:

y = kx

First, find the constant of variation (k) using the initial values:

-16 = k(4)

Then, solve for k:

k = -16/4 = -4

Now that you have the constant of variation (k), you can use it to find x when y = 20:

20 = -4x

Divide both sides by -4:

x = 20 / -4 = -5

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.