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F(n)=f(n-1)+3 such that
f(1)=2
Answer:
Step-by-step explanation:
x-y=7
-3x+9y=-39
Divide the second equation by 3
-x +3y = -13
Add this to the first equation
x-y=7
-x +3y = -13
----------------------
0x +2y = -6
Divide by 2
2y/2 = -6/2
y = -3
Now find x
x-y = 7
x -(-3) = 7
x+3 = 7
Subtract 3 from each side
x = 4
(4,-3)
Or by substitution
x-y=7
solve for x
x = 7+y
-3x+9y=-39
Substitute y+7 in for x
-3(7+y) +9y = -39
Distribute
-21 -3y +9y = -39
Combine like terms
-21 +6y = -39
Add 21 to each side
6y = -18
1 coin is 4 ways
2 coins is 4*3 ways
3 coins is 4*3*2 ways
4 coins is 4*3*2*1 ways
so total is 4+12+24+24=64 sums
Answer:
y = -3/2x + 3
Step-by-step explanation:
y = -3/2x + 3
