Question

Use the equation of the exponential function whose graph passes through the points (0,-2) and (2,-50) to find the value of y when x = -2.

I know the formula is y=ab^x but I don't know what numbers to plug in.

Any help would be great.

Thanks.

Answer 1

first sub in (0,-2) to get
-2 = ab^0, but b^0 = 1
so a=-2
so far we have

y = -2b^x

now use the other point (2,-50)
-50 = -2(b^2)
b^2 = 25
b= ±5
however in exponentional equations the base is usually positve, so now you have

y = -2(5^x)

sub in x=-2 and you got it.