Wednesday, May 21, 2014

Differentiate the exponential function


Write the given equation in point-slope form


Simplify the given radical expression


assuming that cos(theta)=2/7 for an acute angle theta, find sin(theta)

Given:
cos%28theta%29=2%2F7
the fastest way is to use the pythagorean identity:
sin%28theta%29=sqrt%281-cos%28theta%29%5E2%29=sqrt%281-%282%2F7%29%5E2%29

which simplifies to...

%283%2Asqrt%285%29%29%2F7

Simplify with out using a calculator the square root of 704.

factorization can be done by successive division by the prime numbers:
704=352%2A2=176%2A2%5E2=88%2A2%5E3=44%2A2%5E4=22%2A2%5E5=11%2A2%5E6
Now we employ the properties of square roots:



:)

One number is 5 greater than another number. their sum is equal to 5 times their difference. Find the numbers.

1)x=y+5
2)x+y=5(x-y)

1) tells us x-y=5
therefore we can repalce x-y with 5 in 2)
new system:
x+y=25
x-y=5 


adding the two equations...

2x=30

x=15
so...

y=10

What is the inverse function of (2x-1)/(x-3)

y=%282x-1%29%2F%28x-3%29
y%28x-3%29=%28x-3%29%282x-1%29%2F%28x-3%29
xy-3y=2x-1
xy-2x=3y-1
x%28y-2%29=3y-1

x=%283y-1%29%2F%28y-2%29
so the inverse function is:

g%28x%29=%283x-1%29%2F%28x-2%29

Solve: log3(x+3)+log3(x-3)=3

log%283%2C%28x%2B3%29%28x-3%29%29=3

3%5Elog%283%2C%28x%2B3%29%28x-3%29%29=3%5E3

x%5E2-9=27
x%5E2=36
x=6 <--other solution is extraneous

Solve the compound inequality |3x-9| < 15 AND |2x-3| > 5

1)
-15 < 3x-9 < 15
-15+9 < 3x < 15+9
-6 < 3x < 24
-2 < x < 8
(-2,8)

2)
2x-3 < -5 or 2x-3 > 5
2x < -2 or 2x > 8
x < -1 or x > 4
(-oo,-1)U(4,oo)


intersection:
(-2,-1) U (4,8)

Use rational exponents to rewrite as a single radical expression. ∛9 √2

Find the value of x: log6 (5x + 9)= 4

6%5Elog%286%2C%285x%2B9%29%29=6%5E4
5x%2B9=6%5E4
5x=1287
x=1287%2F5

{x + y = 9, 1/x + 1/y = 1/2} Find x and y.

1%2Fx%2B1%2Fy=1%2F2
leads to
%28x%2By%29%2F%28xy%29=1%2F2
but x%2By=9
so
9%2F%28xy%29=1%2F2
this means
y=18%2Fx

which leads to
x%2B18%2Fx=9
x%5E2-9x%2B18=0
so that x=3 or x=6
then we can see:
{ (3,6), (6,3) }

The variables x and y satisfy the equation y=A(b^-x), where A and b are constants. The graph of ln y against x is a straight line passing through the points (0, 1.3) and (1.6, 0.9). Find the values of A and b, correct to 2 decimal places.

y=A%2Fb%5Ex
1.3=A%2Fb%5E0
A=1.30

so this means
0.9=1.3%2Fb%5E1.6
and so
b=1.26

y=1.30%2F1.26%5Ex

Is this sequence geometric or arithmetic or neither: 3,5,9,15 ?

9-5=4
5-3=2
so it is not arithmetic

15/9=5/3
9%2F5++%3C%3E+5%2F3
so it is not geometric either
... so neither

If a person invested a third of her money at 6% and two thirds at 9% and received $450 in interest, find the total money invested.

450=%281%2F3%29%28x%29%280.06%29%2B%282%2F3%29%28x%29%280.09%29
x=5625