A geometric series has three terms. The sum of the three terms is 42. The third term is 3.2 times the sum of the other two. What are the terms?
Let the series be
a, ax, ax²
"The third term is 3.2 times the sum of the other two"
means
ax²/(a+ax)=3.2
cross multiply:
ax²=3.2(a+ax)
cancel common factor a (≠0) & multiply by 10
10x²-32x-32=0
=>x=4 or x= -4/5
Reject solution where |x|<1
x=4, or
"The sum of the three terms is 42" means
a(1+4+16)=42
a=2
So the terms are 2, 8, 32
Thanks for your help :D
by the way did you multiply the equation by 10 to get rid of the decimal to get a whole number?
Yes, it makes life a little easier.
I love integers! :)