Find the value of a if the graph of the exponential function y = a · 2^x passes through the point (3, 128).
Select one:
a. 2
b. 4
c. 8
d. 16

Question

Find the value of a if the graph of the exponential function y = a · 2^x passes through the point (3, 128).
Select one:
a. 2
b. 4
c. 8
d. 16

zepdrix · Answer

Hey there :)
$$\Large\rm y=a\cdot 2^x$$So we pass through the point $\Large\rm (x,y)=(3,128)$
Let's plug it in and solve for a,

zepdrix · Answer

$$\Large\rm 128=a\cdot 2^3$$$$\Large\rm 128=a\cdot 8$$Can you finish it up from there? :)

anonymous · Answer

wouldnt it be 128=a*6 not 8

zepdrix · Answer

Ah let's be careful with our powers! ^^$$\Large\rm 2^3=\quad 2\cdot2\cdot2=\quad 4\cdot2=\quad 8$$

anonymous · Answer

oh yes
so it would be D 16

zepdrix · Answer

yay good job!