I need help with that question thank you

Find f(3) if f(x)=-3x-6

Nikitich [7]

Answer:

-3(3)-6=-15

Step-by-step explanation:

6 0

3 years ago

The sum of first three terms of a finite geometric series is -7/10 and their product is -1/125. [Hint: Use a/r, a, and ar to rep

Alchen [17]

Ooh, fun

geometric sequences can be represented as
$a_n=a(r)^{n-1}$
so the first 3 terms are
$a_1=a$
$a_2=a(r)$
$a_2=a(r)^2$

the sum is -7/10
$\frac{-7}{10}=a+ar+ar^2$
and their product is -1/125
$\frac{-1}{125}=(a)(ar)(ar^2)=a^3r^3=(ar)^3$

from the 2nd equation we can take the cube root of both sides to get
$\frac{-1}{5}=ar$
note that a=ar/r and ar²=(ar)r
so now rewrite 1st equation as
$\frac{-7}{10}=\frac{ar}{r}+ar+(ar)r$
subsituting -1/5 for ar
$\frac{-7}{10}=\frac{\frac{-1}{5}}{r}+\frac{-1}{5}+(\frac{-1}{5})r$
which simplifies to
$\frac{-7}{10}=\frac{-1}{5r}+\frac{-1}{5}+\frac{-r}{5}$
multiply both sides by 10r
-7r=-2-2r-2r²
add (2r²+2r+2) to both sides
2r²-5r+2=0
solve using quadratic formula
for $ax^2+bx+c=0$
$x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}$
so
for 2r²-5r+2=0
a=2
b=-5
c=2

$r=\frac{-(-5) \pm \sqrt{(-5)^2-4(2)(2)}}{2(2)}$
$r=\frac{5 \pm \sqrt{25-16}}{4}$
$r=\frac{5 \pm \sqrt{9}}{4}$
$r=\frac{5 \pm 3}{4}$
so
$r=\frac{5+3}{4}=\frac{8}{4}=2$ or $r=\frac{5-3}{4}=\frac{2}{4}=\frac{1}{2}$

use them to solve for the value of a
$\frac{-1}{5}=ar$
$\frac{-1}{5r}=a$
try for r=2 and 1/2
$a=\frac{-1}{10}$ or $a=\frac{-2}{5}$

test each
for a=-1/10 and r=2
a+ar+ar²= $\frac{-1}{10}+\frac{-2}{10}+\frac{-4}{10}=\frac{-7}{10}$
it works

for a=-2/5 and r=1/2
a+ar+ar²= $\frac{-2}{5}+\frac{-1}{5}+\frac{-1}{10}=\frac{-7}{10}$
it works

both have the same terms but one is simplified

the 3 numbers are $\frac{-2}{5}$ , $\frac{-1}{5}$ , and $\frac{-1}{10}$

6 0

3 years ago

Please help on this ill give braneliest

horsena [70]

Answer:

-2.5

Step-by-step explanation:

25/-10 = -2.5

20/-8 = 2.5

10/-4 = 2.5

-5/2 = 2.5

so the answer is -2.5

Can I pls have brainliest

8 0

2 years ago

What pattern do you see in the powers of 4?

Over [174]

All of them are even numbers. You will not find a power of 4 that is an odd number. Also, all of the numbers have a 4 or a 6 or both. For example,
4^3= 64

4^8= <span>65536

I hope this helps:)</span>

8 0

3 years ago

Read 2 more answers

Kirby is four miles from the train station, from which a train is due to leave in 56 minutes. Kirby is walking along at 3 mph, a

Luda [366]

Let's assume that Kirby walks with a speed
$v_1 = 3 mph$
for a time $t_1$ , and that he runs with a speed
$v_2 = 12 mph$
for a time $t_2$ .

The total time available for Kirby to catch the train is:
$t=56 min = 0.93 h$
and this must be equal to the sum of the two times t1 and t2:
$0.93 = t_1 + t_2$

The distance Kirby should cover is
$S=4 m$
and this should be equal to the sum of the distances covered by walking and by running:
$4 = S_1 + S_2 = v_1 t_1 + v_2 t_2 = 3 t_1 + 12 t_2$

So we have a system of 2 equations:
$0.93 = t_1 + t_2$
$4 = 3 t_1 + 12 t_2$

If we solve the system, we find:
$t_1 = 0.80 h = 48 min$
$t_2 = 0.13 h = 8 min$

So, Kirby needs to run at least for 8 minutes in order to catch the train.

6 0

3 years ago