1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
velikii [3]
3 years ago
14

Expand (3x+7)(3x-7) =

Mathematics
2 answers:
saveliy_v [14]3 years ago
8 0

Answer:

9 {x}^{2}  - 49

Step-by-step explanation:

Do FOIL, first outside inside last

3x × 3x = 9x^2

3x × -7 = -21x

7 × 3x = 21x

7 × -7 = -49

9 {x}^{2}   - 21x + 21x - 49 \: midde \: cancels \: each \: other \: out

So it would just be 9x^2 - 49

Tamiku [17]3 years ago
8 0

(3x + 7)(3x - 7) =

= 9x² + 21x - 21x - 49

= 9x² - 49

You might be interested in
Like b and c are parallel what is the measure of <2
Vadim26 [7]
C
Hope this helps 8)
5 0
3 years ago
How many minutes are there in a day?
RoseWind [281]
1440

because yea

hehehehehehehehehee
5 0
3 years ago
Read 2 more answers
If the retail price of an item is 70$ and its markuped by35%, what is its wholesale price?
sveta [45]

Answer:

94.50$

Step-by-step explanation:

4 0
3 years ago
Model how to factor the polynomial 2x^3-8x^2+3x-12
san4es73 [151]
2x^3-8x^2+3x-12=2x^2(x -4)+3(x -4)=(x -4)(2x^2+3)


6 0
3 years ago
Newton's law of cooling is:
Mnenie [13.5K]

Answer:

t = \frac{ln(\frac{21}{59})}{-0.15}=6.887 hr

So it would takes approximately 6.9 hours to reach 32 F.

Step-by-step explanation:

For this case we have the following differential equationÑ

\frac{du}{dt}= -k (u-T)

We can reorder the expression like this:

\frac{du}{u-T} = -k dt

We can use the substitution w = u-T and dw =du so then we have:

\frac{dw}{w} =-k dt

IF we integrate both sides we got:

ln |w| = -kt +C

If we apply exponential in both sides we got:

w = e^{-kt} *e^c

And if we replace w = u-T we got:

u(t)= T + C_1 e^{-kt}

We can also express the solution in the following terms:

u(t) = (T_i -T_{amb}) e^{kt} +T_{amb}

For this case we know that k =-0.15 hr since w ehave a cooloing, T_{i}= 70 F, T_{amb}=11F, we have this model:

u(t) = (70-11) e^{-0.15t} +11

And if we want that the temperature would be 32F we can solve for t like this:

32 = 59 e^{-0.15 t} +11

21=59 e^{-0.15 t}

\frac{21}{59} = e^{-0.15 t}

If we apply natural logs on both sides we got:

ln (\frac{21}{59}) =-0.15 t

t = \frac{ln(\frac{21}{59})}{-0.15}=6.887 hr

So it would takes approximately 6.9 hours to reach 32 F.

7 0
3 years ago
Other questions:
  • On a recent trip, sarah's car traveled 20 mph faster on the first 110 miles than it did on the remaining 80 miles. the total tim
    12·1 answer
  • Share £12 in the ratio of 3:2:1
    9·1 answer
  • Find the degree of this monomial. -5a^8
    14·1 answer
  • Assume that the city of Dallas is in the state of Texas. Which statement is definitely NOT true?
    7·1 answer
  • Create three fractions whose product is -5/24. You may only use fractions between -8/9 to 8/9 and you can only use a fraction on
    12·1 answer
  • Employee working at Electronics store and $4560 for working eight months during the summer at the three month mark how much did
    5·1 answer
  • Solve for x: -56= 8x
    9·1 answer
  • Which of the following expressions is written in scientific notation
    8·1 answer
  • Write an equation that expresses the following relationship.
    15·1 answer
  • Find the slope of<br> the line.<br> [?]<br> Give your answer as<br> a fraction in simplest<br> form.
    9·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!