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2 years ago

Plz help 7x^2 - 6(x + 3)

Mathematics

1 answer:

max2010maxim [7]2 years ago

4 0

Answer:

7x² - 6x - 18

Step-by-step explanation:

7x² - 6(x + 3)

multiply with -6

7x² - 6x - (6 × 3)

evaluate

= <u>7x² - 6x - 18</u>

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A sample of bacteria is being eradicated by an experimental procedure. The population is following a pattern of exponential deca

77julia77 [94]

Answer:

There will be 50 bacteria remaining after 28 minutes.

Step-by-step explanation:

The exponential decay equation is

$N=N_0e^{-rt}$

N= Number of bacteria after t minutes.

$N_0$ = Initial number of bacteria when t=0.

r= Rate of decay per minute

t= time is in minute.

The sample begins with 500 bacteria and after 11 minutes there are 200 bacteria.

N=200

$N_0$ = 500

t=11 minutes

r=?

$N=N_0e^{-rt}$

$\therefore 200=500e^{-11r}$

$\Rightarrow e^{-11r}=\frac{200}{500}$

Taking ln both sides

$\Rightarrow ln| e^{-11r}|=ln|\frac{2}{5}|$

$\Rightarrow {-11r}=ln|\frac{2}{5}|$

$\Rightarrow r}=\frac{ln|\frac{2}{5}|}{-11}$

To find the time when there will be 50 bacteria remaining, we plug N=50, $N_0$ = 500 and $r}=\frac{ln|\frac{2}{5}|}{-11}$ in exponential decay equation.

$50=500e^{-\frac{ln|\frac25|}{-11}.t}$

$\Rightarrow \frac{50}{500}=e^{\frac{ln|\frac25|}{11}.t}$

Taking ln both sides

$\Rightarrow ln|\frac{50}{500}|=ln|e^{\frac{ln|\frac25|}{11}.t}|$

$\Rightarrow ln|\frac{1}{10}|={\frac{ln|\frac25|}{11}.t}$

$\Rightarrow t= \frac{ln|\frac{1}{10}|}{\frac{ln|\frac25|}{11}.}$

$\Rightarrow t= \frac{11\times ln|\frac{1}{10}|}{{ln|\frac25|}}$

$\Rightarrow t\approx 28$ minutes

There will be 50 bacteria remaining after 28 minutes.

3 0

3 years ago

Solve the simultaneous equations 2x + y = 5 and 2y = x – 10.

Black_prince [1.1K]

X = 4
The first equation can be substituted into the second one. It would be: 2(-2x+5)=x-10 and after solving it, x = 4

7 0

3 years ago

Read 2 more answers

The diagram below shows a pennant in the shape of an isosceles triangle. The equal sides each measure 13. The altitude is x + 7

Kisachek [45]

Answer: The length of the base is 10.

Step-by-step explanation:

You can draw an isosceles triangle like the one shown attached.

An isosceles triangle has two equal sides. Then, you can divide it into two right triangles, where the base of each one of them will be:

$b'=\frac{2x}{2}=x$

The hypotenuse of each right triangle shown is 13 and the other legs are (x+7) and x, therefore you can apply the Pythagorean Theorem:

$13^2=x^2+(x+7)^2$

Simplify the expression:

$169=x^2+(x^{2}+2(x)(7)+7^2)\\169=x^{2}+x^{2}+14x+49\\0=2x^{2}+14x-120$

Use the quadratic formula, where:

$a=2\\b=14\\c=-120$

$x=\frac{-b\±\sqrt{b^2-4ac}}{2a}$

Then:

$x=\frac{-14\±\sqrt{14^2-4(2)(-120)}}{2+2}$

$x_1=5\\x_2=-12$

Choose the positive value, because lengths are not negative.

Substitute the value of x into the base 2x. Therefore, the answer is:

$b=2x=2(5)=10$

7 0

3 years ago

Which of these expressions shows a correct way to set up the slope formula for the line that passes through the points (5, 0) an

vaieri [72.5K]

Answer:

Step-by-step explanation:

its c because if we input the numbers into the slope formula y2 - y1 over x2 - x1 it equals -6 - 0 over 6 - 5

3 0

3 years ago

If (x) = x+8 and g(x) = -4x-3, find (f+ g)(x).

Ede4ka [16]

Answer:

Answer=B

(f+g)(x)=-3x-5

Step-by-step explanation:

f(x)=x+8.

g(x)=-4x-3.

(f+g)(x) means f(x)+g(x),So

(x+8)+(-4x-3)

(add all same terms together)

=(x+(-4x))+(8+(-3))

=-3x+5

so,

(f+g)(x)=-3x+5

8 0

3 years ago