Sunday, December 29, 2013

find the complement and supplement of an angle with the given measure. a.)10° 10' 30" , b.)1° 40' 19"

a)
90°=89° 59' 60"
so...
complement:
89° 59' 60"-10° 10' 30"=
79° 49' 30"
supplement:
169° 49' 30"
b)
complement
89° 59' 60"-1° 40' 19"=
88° 19' 41"
supplement:
178° 19' 41"

Saturday, December 28, 2013

Solve: 3(4^2x)+5(4^x)-2=0

3%284%5E%282x%29%29%2B5%284%5Ex%29-2=0
u=4%5Ex
3u%5E2%2B5u-2=0
%283u-1%29%28u%2B2%29=0
u+2 is extraneous, assuming all solutions are to be real
3%2A4%5Ex=1
4%5Ex=1%2F3

Taking log base 4 of both sides...


Friday, December 27, 2013

Wednesday, December 25, 2013

The length of a football field is 180 feet more than its width. If the perimeter of the field is 1,060 feet, find the length of the field

1)
P=2%28l%2Bw%29=1060
so
l%2Bw=530
2)
l=w%2B180
so
l-w=180

adding equations...
2l=710
l=355

Alan participated in a car race in which he had to cover a distance of at least 50 kilometers. He had fuel in his car for a maximum distance of 53 kilometers. If the distance is given by S(t)=3t+47 , where (t) is the time in hours, find the minimum and maximum number of hours for which Alan can drive his car.

S%28t%29=3t%2B47=53
so
3t%2B47-47=53-47=6
t=2
In general his limits are:
0+%3C=+t+%3C=+2
but assuming he wants to stay in the race:
3t%2B47-47=50-47=3
t=1
and his limits are:
1%3C=t+%3C=2

Find the difference quotient (f(x+h)-f(x))/h , where h is not equal to zero for the function below: f(x)=5x^2 +3x Simplify the answer as much as possible.


so that means
f%28x%2Bh%29-f%28x%29=5x%5E2%2B10xh%2B5h%5E2%2B3x%2B3h-5x%5E2-3x=10xh%2B5h%5E2%2B3h

furthermore
%28f%28x%2Bh%29-f%28x%29%29%2Fh=%2810xh%2B5h%5E2%2B3h%29%2Fh=10x%2B3%2B5h

AP exam in math has a mean score of 73 with a standard deviation of 7.8. If one student is randomly selected, find the probability that the student's test score is less than 70.

Tuesday, December 24, 2013

find the smallest square number that is divisible by 6, 18 and 21?

6=2*3
18=2*3^2
21=3*7 
To be a square we need all prime factors squared (at least once in general):
n=((2)(3)(7))^2=1764

B=(a-c)/( d-e) make e the subject of the formula

%28d-e%29B%2FB=%28%28a-c%29%2F%28+d-e%29%29%28d-e%29%2FB
d-e=%28a-c%29%2FB
e=d-%28a-c%29%2FB

Solve by substitution: {6x+2y=11, 4x+y=6}.

6x+2(6-4x)=11
6x+12-8x=11
-2x=-1
x=1/2
y=6-4(1/2)=6-2=4
y=4
solution: (1/2, 4)

Find the average rate of change for the function between the given values. f(x) = sqrt 2x ; from 2 to 8

A%28x%29=%28f%28b%29-f%28a%29%29%2F%28b-a%29
A%28x%29=%28sqrt%2816%29-sqrt%284%29%29%2F%288-2%29=%284-2%29%2F6=1%2F3 

A painter can finish painting a house in 6 hours Her assistant takes 8 hours to finish the same job How long would it take for them to complete the job if they were working together?

rates can be added:
1/6+1/8=1/t
4/24+3/24=1/t
1/t=7/24
t=24/7 =3 3/7 hr

Saturday, December 14, 2013