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Answer:

Step-by-step explanation:
y′′ + 4y′ − 21y = 0
The auxiliary equation is given by
m² + 4m - 21 = 0
We solve this using the quadratic formula. So

So, the solution of the equation is

where m₁ = 3 and m₂ = -7.
So,

Also,

Since y(1) = 1 and y'(1) = 0, we substitute them into the equations above. So,


Substituting A into (1) above, we have

Substituting B into A, we have

Substituting A and B into y, we have

So the solution to the differential equation is

Answer:
Your answer is correct. The series is a geometric series with common ratio -1/4 and first term 40. So each term is:
an = 40 (-1/4)^(n−1)
So the sum of the first 10 terms is:
∑(n=1 to 10) [ 40 (-1/4)^(n−1) ]
Answer:
-2y + 6 = -12
Step-by-step explanation:
well the answer is 9, y=9 :)
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