Posted by **Claudia** on Thursday, August 8, 2013 at 10:48pm.

A diagram shows a straight line graph of In y against x,passing through the point (0,2) and having gradient -3/2 .

The variables x and y are connected by the equation y=pq^x ,where p and q are constants

Find

(i)the value of p and of q ,to one decimal place

(ii)the equation relating x and y

- math -
**Steve**, Friday, August 9, 2013 at 12:02am
y = pq^x

lny = lnp + x lnq

2 = lnp + 0 lnq

p = e^2

1/y y' = lnq

y' = y ln q

-3/2 = 2 lnq

lnq = -3/4

q = e^(-3/4)

y = e^2 e^(-3x/4)

- math -
**Claudia**, Friday, August 9, 2013 at 12:24am
Can be more specific? still do not understand ...

The answer for part (ii) should be y=7.4(0.2)^2

and the values of q is o.2 ..

- math -
**Steve**, Friday, August 9, 2013 at 12:36am
sorry. Guess I should not have given that last line, but the values for p and q were given...

p = e^2 = 7.4

q = e^(-3/2) = 0.2

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