Answer: x = 1, y = -2
Step-by-step explanation:
-9x+2y=-13
x= 13/9 + 2/9y
2x-9y=20
2(13/9+2/9y)-9y=20
<em>Substitute y with -2.</em>
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x= 13/9+2/9(-2)
<em>After solving you'll see that 1 is a possible solution for x.</em>
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Check your answer
-9x+2y=-13
-9x1+2(-2) = -13
2x-9y=20
2x1-9(-2) = 20
-13 = -13
20 = 20
Therefore, x=1 and y=-2
Answer:
f(n) = -n^2 -3n +5
Step-by-step explanation:
Suppose the formula is ...
f(n) = an^2 +bn +c
Then we have ...
f(1) = 1 = a(1^2) +b(1) +c
f(2) = -5 = a(2^2) +b(2) +c
f(3) = -13 = a(3^2) +b(3) +c
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Here's a way to solve these equations.
Subtract the first equation from the second:
-6 = 3a +b . . . . . 4th equation
Subtract the second equation from the third:
-8 = 5a +b . . . . . 5th equation
Subtract the fourth equation from the fifth:
-2 = 2a
a = -1
Then substituting into the 4th equation to find b, we have ...
-6 = 3(-1) +b
-3 = b
and ...
1 = -1 +(-3) +c . . . . . substituting "a" and "b" into the first equation
5 = c
The formula is ...
f(n) = -n^2 -3n +5
Answer:
121
Step-by-step explanation:121 ! just got it right.
