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damaskus [11]
3 years ago
8

Solve the system using substitution. Show all work

Mathematics
1 answer:
kramer3 years ago
6 0

Answer:

x = -2 , y = 3

Step-by-step explanation:

Solve the following system:

{4 x + 5 y = 7

y = 3 x + 9

Hint: | Perform a substitution.

Substitute y = 3 x + 9 into the first equation:

{4 x + 5 (3 x + 9) = 7

y = 3 x + 9

Hint: | Expand the left hand side of the equation 4 x + 5 (3 x + 9) = 7.

4 x + 5 (3 x + 9) = (15 x + 45) + 4 x = 19 x + 45:

{19 x + 45 = 7

y = 3 x + 9

Hint: | Choose an equation and a variable to solve for.

In the first equation, look to solve for x:

{19 x + 45 = 7

y = 3 x + 9

Hint: | Isolate terms with x to the left hand side.

Subtract 45 from both sides:

{19 x = -38

y = 3 x + 9

Hint: | Solve for x.

Divide both sides by 19:

{x = -2

y = 3 x + 9

Hint: | Perform a back substitution.

Substitute x = -2 into the second equation:

Answer:  {x = -2 , y = 3

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(a) The projectile remains in the air for 10 seconds

(b) It travels a horizontal distance of 600 meters

Step-by-step explanation:

A projectile is fired at such an angle that

1. The vertical  component of its velocity is 49 m/sec

2. The horizontal  component of its velocity is 60 m/sec

We need to find:

(a) How long the projectile remains in the air

(b) The horizontal distance it travels

∵ The vertical distance y = u_{y} t - \frac{1}{2} g t², where

u_{y} is the vertical  component of its velocity, g is the acceleration

of gravity and t is the time

∵ y = 0 ⇒ it return to the same initial height

∵ u_{y} = 49 m/s

∵ g = 9.8 m/s²

- Substitute these values in the rule above

∴ 0 = 49 t - \frac{1}{2} (9.8) t²

∴ 0 = 49 t - 4.9 t²

- Take t as a common factor

∴ 0 = t (49 - 4.9 t)

- Equate each term by 0

∴ t = 0 ⇒ at initial position

∴ 49 - 4.9 t = 0

- Add 4.9 t to both side

∴ 49 = 4.9 t

- Divide both sides by 4.9

∴ t = 10 seconds

(a) The projectile remains in the air for 10 seconds

∵ The horizontal distance = u_{x} t, where u_{x} is the

   horizontal component of its velocity

∵ u_{x} = 60 m/sec

∵ t = 10 seconds

∴ x = 60 × 10 = 600 meters

(b) It travels a horizontal distance of 600 meters

Learn more:

You can learn more about the component of velocity in brainly.com/question/4464845

#LearnwithBrainly

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