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3 years ago

Help me with my test

Mathematics

2 answers:

zavuch27 [327]3 years ago

5 0

Answer:

B. -8

Step-by-step explanation:

first find k: plug 3 and -2 into the function

$3=2(-2)^2-5(-2)+k\\3=2(4)+10+k\\3=18+k\\k=-15$

then plug -1 into $2x^2-5x-15$

$2(-1)^2-5(-1)-15\\= 2(1)+5-15\\=7-15\\=-8$

h(-1) = -8

geniusboy [140]3 years ago

4 0

$- 8.$

Step-by-step explanation:

$h(x) = 2 {x}^{2} - 5x + k$

If h(-2) = 3.

Then, h(-1) =

$h( - 1) = 2 {( - 1)}^{2} - 5( - 1) + k$

$h( - 1) = 2 + 5 + k$

$h( - 1) = 7 + k$

$- 1 - 7 = k$

$- 8 = k$

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4 years ago

Question 2<br> Solve by substitution.<br> 2x – 10y = 14<br> 2x + 6y = -2

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3 years ago

Joe can cut and split a cord of firewood in 3 fewer hours than Dwight can. When they work together, it takes them 2 hours. How

aalyn [17]

Answer:

Dwight will take 6 hours to finish the job alone and Joe will take 3 hours to finish the job alone.

Step-by-step explanation:

Let us assume the time taken by Dwight to split a cord of firewood = K hrs

So, the per hour rate of Dwight = $(\frac{1}{K})$

As, Joe uses 3 LESS hours then Dwight.

So, the time taken by Joe to split a cord of firewood = (K- 3) hrs

So, the per hour rate of Joe = $(\frac{1}{K-3})$

Now, when both of them wok together, it takes them 2 hours.

So, the per hour rate of BOTH of them = $(\frac{1}{2})$

⇒ Per hour rate of ( Dwight + Joe) = $(\frac{1}{2} )$

$\implies (\frac{1}{K}) + (\frac{1}{K-3}) = (\frac{1}{2})$

Now, solving for the value of K , we get:

$(\frac{1}{K}) + (\frac{1}{K-3}) = (\frac{1}{2})\\\implies \frac{(K-3) + K}{K (K-3)} = (\frac{1}{2})\\\implies 2(2K -3) = K^2 - 3K\\\implies k^2 - 3K -4K +6 = 0\\\implies K^2 - 7K + 6= 0\\\implies K^2 - 6K - K + 6= 0\\\implies K(K-6) -1(K - 6)= 0\\\implies (K-6)(K-1) = 0$

Implies either K = 6 Or K = 1

But if K = 1, (K-3) = 1- 3 = -2 hours would be A CONTRADICTION.

⇒ K = 6 hours

Hence, Dwight will take 6 hours to finish the job alone and Joe will take (k-3) = (6-3) = 3 hours to finish the job alone.

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3 years ago