The first and third term of a Gp are 5 and 80 respectively.what is the 4th term?
in a GP
a = 5
term(3) = ar^2 = 5r^2 = 80
r^2 = 16
r = ± 4
if r = +4 , term(4) = ar^3 = 5(4^3) = 320
if r = -4 , term(4) = ar^3 = 4(-4)^3 = -320
check:
if a = 5, r = 4
first 5 terms are: 5, 20, 80, 320, 1280
if a = 5, r = -4
first 5 terms are: 5, -20, 80, -320, 1280
all the given data fits
a= 5
T3 =ar^2
5r^2=80
5r^2/5=80/5
r^2=16
r=4
r=4=ar^3=5(4)^3=320
answer is 320
correctly
Solve the fist and third of a gp 5 and 80 respectively what is 4th term
Correctly
CORRECTLY
320
you guys are fabulous av been cracking my head's
In GP
A=5
Term (3)=ar^2=5r2=80
R^2=16
R=+-4
If r=4,term(4)=ar^3=5+(4^3)=320
Thanks to all who answered this question please do well to check my working following my teachers sample.
a=T1=5
T1 = 5 = ar^1-1 = ar = 5____¡(equation 1)
T3 = 80 = ar^3-1 = ar^2 = 80 ____¡¡(equation 2)
i/ii(equation 2 divided by equation 1) i.e
ar =5____¡
ar =80___¡¡
ar/ar^2(a will cancel a and r^2 will cancel r and r will be only r) =80/5 = 16
T4=ar^n-1 = ar^3
T4=5(16)^3 = 5 * 4096
T4 =20480.
BUT MY ANSWER IS'NT THE SAME PLEASE CORRECT ME
IT'S REALLY URGENT
THANKS ALOT.
In a G.p
A=5
Term(3)=ar^2=5r^2=80
R^2=16
R=±4
If r=+4,term(4)=ar^3=5+(4^3)=320