Help
oh wait
it's recursive, so you would start with a1 = 2 then apply the rule, which tells you to multiply the term by 3 and subtract 1 to get the next term
then take the result from that operation and then find the next term using the same rule
recursive formulas stink but thankfully we don't use these very often
a1=2 a2=5 a3=14 a4=41 a5=122
good
so for 9 you want to write an arithmetic equation to solve for d
an = a1 + (n-1)d an = 11 a1 = 2 n = 4 solve for d
d=3
awesome, now we use the sum formula
okay
|dw:1510377993846:dw|
since we want n = 50 we will need to find a50 first
use this: an = a1 + (n-1)d to find an when n = 50, keeping the same a1 and d value as before
149/50
a50 = 2 + (50-1)3 = ?
297
ah think I see what the misunderstanding is the 50 in a50 is not treated like a number, it's just a label
149
good, 149
now we go back to our sum formula
|dw:1510378518379:dw|
then find sn using these values
3775
awesome, that's the final answer
for 10, this is what we are given: 3x + 2y = 14 2x - 4y = 4 start by doubling the first eqution
okay
then, you should be able to eliminate y by adding the equations together
wait by doubling do you mean 6x+4y=28
yes
since there's +4y on the top and -4y on the bottom these cancel when you add the equations
12x=112
6x+4y=28 2x - 4y = 4 start by adding the x terms. 6x + 2x = ?
oh we are adding I thought we were multiplying
x=4
as a general rule you can multiply equations by a constant, but not multiply the equations together
yes, x = 4
now solve for y 2x - 4y = 4 when x = 4
y=1
good so (4,1) = your ans
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