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2 years ago

R is the midpoint of AM. If RA = x2 - 16x and MR = 80, find x.

Mathematics

1 answer:

sergij07 [2.7K]2 years ago

3 0

Answer:

x = - 4 or x = 20

Step-by-step explanation:

Given R is the midpoint of AM, then

RA = MR , substitute values

x² - 16x = 80 ( subtract 80 from both sides )

x² - 16x - 80 = 0 ← in standard form

(x - 20)(x + 4) = 0 ← in factored form

Equate each factor to zero and solve for x

x - 20 = 0 ⇒ x = 20

x + 4 = 0 ⇒ x = - 4

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which indeed gives the recurrence you found,

$a_{n+3}=-\dfrac{n-3}{n+3}a_n$

but in order to get anywhere with this, you need at least three initial conditions. The constant term tells you that $a_2=0$ , and substituting this into the recurrence, you find that $a_2=a_5=a_8=\cdots=a_{3k-1}=0$ for all $k\ge1$ .

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2 years ago

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