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3 years ago

Can anyone please help me with this? i need a step by step explanation please! very appreciated:)

Mathematics

2 answers:

d1i1m1o1n [39]3 years ago

8 0

Answer:

x=8 and y=31

Let's solve your system by substitution.

y=5x−9;y=3x+7

Step: Solve y=5x−9for y:

y=5x−9

Step: Substitute5x−9foryiny=3x+7:

y=3x+7

5x−9=3x+7

5x−9+−3x=3x+7+−3x (Add -3x to both sides)

2x−9=7

2x−9+9=7+9(Add 9 to both sides)

2x=16

2x/2=16/2 (Divide both sides by 2)

x=8

Step: Substitute 8 for x in y=5x−9:

y=5x−9

y=(5)(8)−9

y=31 (Simplify both sides of the equation)

Answer:

x=8 and y=31

NOTE: Please give the brainly to the first answer

HOPE THIS HELPS <33333

-Silver

EastWind [94]3 years ago

5 0

Answer:

Step-by-step explanation:

x and y are variables. That means they represent numbers that are unknown. When we solve for x or y, we are trying to find what number the variable represents.

Y is a number that equals both 5x-9 and 3x+7. If it is a number, it can only have one value, so we can say that 5x-9 and 3x+7 have the same value.

In other words, 5x-9 = 3x+7.

Another way of thinking about this step is substitution. y=3x+7, so in the equation y=5x-9, we can replace the y with 3x+7. It will give 3x+7 = 5x-9.

In either case, we have this new equation

5x-9 = 3x+7.

From here it's just simple algebra- subtract 3x from each side

2x -9 = 7

and add 9 to each side

2x = 16

and divide each side by 2.

x = 8.

All these steps work because if two things equal each other, when you do the same thing to both of them (such as add 9), the new values will still equal each other.

Now that we know that x = 8, we can take one of the original equations

y=5x-9

and put 8 in for x.

y=5*(8) -9.

If x represents the value 8, we can obviously switch out x for 8.

Now simplify

y=40 -9

y = 31

Now we know that x = 8 and y = 31.

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Step-by-step explanation:

Given:

- 7 - (-11) expression

We can add or remove only positive numbers on the number line to get it correct, so we need to open the parenthesis. When evaluated we get:

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Kryptonite is a material found on the planet Krypton and has various effects, most importantly on Superman. The most common type

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Answer:

The maximum amount of red kryptonite present is 33.27 g after 4.93 hours.

Step-by-step explanation:

dy/dt = y(1/t - k)

separating the variables, we have

dy/y = (1/t - k)dt

dy/y = dt/t - kdt

integrating both sides, we have

∫dy/y = ∫dt/t - ∫kdt

㏑y = ㏑t - kt + C

㏑y - ㏑t = -kt + C

㏑(y/t) = -kt + C

taking exponents of both sides, we have

$\frac{y}{t} = e^{-kt + C} \\\frac{y}{t} = e^{-kt}e^{C} \\\frac{y}{t} = Ae^{-kt} (A = e^{C})\\y = Ate^{-kt}$

when t = 1 hour, y = 15 grams. So,

$y = Ate^{-kt}\\15 = A(1)e^{-kX1}\\15 = Ae^{-k}$ (1)

when t = 3 hours, y = 30 grams. So,

$y = Ate^{-kt}\\30 = A(3)e^{-kX3}\\30 = 3Ae^{-3k}$ (2)

dividing (2) by (1), we have

$\frac{30}{15} = \frac{3Ae^{-3k}}{Ae^{-k}} \\2 = 3e^{-2k}\\\frac{2}{3} = e^{-2k}$

taking natural logarithm of both sides, we have

-2k = ㏑(2/3)

-2k = -0.4055

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From (1)

$A = 15e^{k} \\A = 15e^{0.203} \\A = 15 X 1.225\\A = 18.36$

Substituting A and k into y, we have

$y = 18.36te^{-0.203t}$

The maximum value of y is obtained when dy/dt = 0

dy/dt = y(1/t - k) = 0

y(1/t - k) = 0

Since y ≠ 0, (1/t - k) = 0.

So, 1/t = k

t = 1/k

So, the maximum value of y is obtained when t = 1/k = 1/0.203 = 4.93 hours

$y = 18.36(1/0.203)e^{-0.203t}\\y = \frac{18.36}{0.203}e^{-0.203X1/0.203}\\y = 90.44e^{-1}\\y = 90.44 X 0.3679\\y = 33.27 g$

So the maximum amount of red kryptonite present is 33.27 g after 4.93 hours.

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