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jonny [76]
3 years ago
11

If y varies directly as x and y-21 when x is 7, find x when y = -5.

Mathematics
2 answers:
alukav5142 [94]3 years ago
8 0

Answer:

X=-5/3

Step-by-step explanation:

<h2>Y=KX where k is constant</h2><h2>y=kx</h2><h2>21=7k divide both sides by 7</h2><h2>to get 3</h2><h2>then equate</h2><h2>to get answer</h2>
klasskru [66]3 years ago
6 0

Step-by-step explanation:

Since, y varies directly as x:

\therefore \: y = kx..(1) \\ (k = constant \: of \: proportionality) \\ at \: y = 21 \: and \: x = 7 \\ 21 = k \times 7 \\ k =  \frac{21}{7}  = 3 \\ plugging \: k = 3 \: in \: equation \: (1) \\ y = 3x..(2) \\ plugging \:  \: y =  - 5  \: in \: (2)\\  - 5 = 3x \\ x =  \frac{ - 5}{3}  \\   \:  \:  \:  \:  \:  \: \huge \red{ \boxed{x =  -  \frac{5}{3} }}

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