kevincourtes
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kevincourtes
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cwrw238
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if y varies directly with x then
y = kx where k is a constant
find k by plugging in the given values of y and x
when y = 3 , x = 2
3 = k * 2
can you find k?
kevincourtes
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@cwrw238 3/2?
cwrw238
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divide both sides of the equation by 2 to find k
right
kevincourtes
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@cwrw238 so the answers D right?
cwrw238
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so now we have
|dw:1366501494754:dw|
kevincourtes
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@cwrw238 can you help me with this one?
cwrw238
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can u see what i've done i've substituted 3/2 for k
now to find y when x = 3
plug in 3 for x and work out the value of y
kevincourtes
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@cwrw238 9/2?
cwrw238
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right
cwrw238
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if y varies directly by x
y = kx
and k = y/x
kevincourtes
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@cwrw238 i dont understand the 2nd problem
cwrw238
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now plug in the values of x and y
y = -3 and x = 1
k = -3 / 1 = -3
y = -9 and x = 3
k = -9/3 = -3
also k = -15 / 5 = -3
so is this varying direct;y?
kevincourtes
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@cwrw238 no?
cwrw238
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these values of y and x do satisfy the relation y = kx
which is direct variation
do you see that?
cwrw238
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k - -3 in all 3 cases
kevincourtes
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@cwrw238 ohhhh okay so the answer would be A?
cwrw238
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right
there are 2 types of variation
direct where y = kx
and indirect where y = k / x
kevincourtes
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@cwrw238 thanks
kevincourtes
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@cwrw238 also can you help me with this last one?