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maria [59]
3 years ago
11

Solve the system of equations. X = 3y + 4 4x - 12y = 16 please help :(

Mathematics
1 answer:
mario62 [17]3 years ago
8 0
Omg this is relly harf
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A rock was thrown from the top of a cliff such that its distance above sea level was given by s(t)= at² + bt + c, where t is the
frutty [35]

Answer:

<h2>a) a = -3, b = 18, c = 48; </h2><h2>s(t) = -3t²+18t+48</h2><h2>b) 48m</h2><h2>c) 8secs</h2>

Step-by-step explanation:

The question is incomplete. Here is the complete question.

'A rock was thrown from the top of a cliff such that its distance above sea level was given by s(t)=at²+bt+c, where t is the time in seconds after the rock was released. After 1 second the rock was 63 m above sea level, after 2 seconds 72 m, and after 7 seconds 27 m. a. Find a, b and c and hence an expression for s(t). b. Find the height of the cliff. c. Find the time taken for the rock to reach sea level.'

Given the equation of the distance modelled as s(t)=at²+bt+c

If after 1 second the rock was 63 m, then 63 = a+b+c

If after 2 seconds, the distance was 72 m then 72 = 4a+2b+c

Also if after 7 seconds, the distance is 27 m, then 27 = 49a+7b+c

i) Solving the 3 equations simultaneously to get a, b and c we have;

a+b+c = 63 ... 1

4a+2b+c = 72 ...2

49a+7b+c = 27 ...3

Subtracting 2 from 1 and 3 from 2 we will generate 2 new equations as shown;

eqn 2- eqn1: 3a + b = 9...4

eqn 3- eqn 2: 45a + 5b = -45

eqn 3- eqn 2: 9a+b = -9 ... 5

solving 4 and 5 simultaneously

3a + b = 9 ...4

9a+b = -9 ... 5  

Taking the difference of 4 and 5 we have

6a - -9-9

6a = -18

a = -3

substituting a = -3 into equation 4 to get b we have;

3(-3)+b = 9

-9 + b = 9

b = 9+9

b = 18

substituting a = -3 and b = 18 into equation 1 to get c we have;

-3+18+c = 63

15+c = 63

c = 48

a = -3, b= 18 and c = 48

The distance function will be s(t) = -3t²+18t+48

ii) If the height of the cliff is modelled by the equation  s(t)=at²+bt+c

The height of the cliff is at when t = 0

s(0) = -3(0)²+18(0)+48

s(0) = 48m

The height of the cliff is 48m

iii) At the sea level, the height of the rock will be 0m, substituting this into the modeled equation for the height to get the time we have;

s(t)=at²+bt+c

0 = -3t²+18t+48

3t²-18t-48 = 0

t² - 6t - 16 =0

t² - 8t+2t - 16 = 0

t(t-8)+2(t-8) = 0

(t+2)(t-8) = 0

t = -2 or 8

Taking the positive value of the time, t = 8secs

Time taken for the rock to reach sea level is 8secs

7 0
3 years ago
Y=x + 4 and 2y = -2x - 8
Sphinxa [80]
Socratic is a really good app for these type of questions! I definitely recommend. For science too!

5 0
3 years ago
There are 2 kids of the age 14 what is the percentage of the students that are 14?
lys-0071 [83]

Answer:

7% my answer i think if im mistake please dont report me

4 0
2 years ago
Read 2 more answers
Find the value of 5x+6 when x=-2
jeka57 [31]

Answer:

-4

Step-by-step explanation:

5 times negative -2 is -10 and you just add 6 so the answer is -4

5 0
3 years ago
Read 2 more answers
Y=−2x+1<br> x−3y=11 find the solution using elimination.
yawa3891 [41]

Answer:

Step-by-step explanation:

Using first equation in the second gives you

x-3(-2x+1)=11

x+6x-3=11

7x-3=11

7x=14

x=2, making y=-2x+1 become

y=-2(2)+1

y=-4+1

y=-3 so the solution is the point

(2,-3)

3 0
2 years ago
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