# Posts by erica

Total # Posts: 615

**pre-calc**

solve each system of equations using matrices x+2y-3z=0 2x-4y=z=-7 -2x+2y-3z=4 I don't see how it is possible to even attempt a matrix on this text oriented site.

**pre-calc**

find real numbers a,b,c so that the graph of the function y=ax^2+bx+c contains the points (-11,4), (2,3) , and (0,1) Write three equations, with each point in one. Then solve the three equations.

**pre-calculus**

Solve eacy system of inequalities. If the system has no solution, say that it is inconsistant. x -y -z = 1 2x +3y +z = 2 3x +2y = 0 add the top two equations. 2x+2y =3 That is inconsistent with the last equation.

**Pre-Calculus**

The logistic growth model p(t)=0.90/1+3.5e^-0.339t relates the proportion of new personal computers sold @ Best Buy that have Intel's latest coprecessor t months after it has been introduced. a) what proportion of new personal computers sold @ Best Buy will have Intel'...

**Pre-Calculus**

A culture of bacteria obeys the law of unlimited growth. If 500 bacteria are present initially and there are 800 after 1 hour, how many will be present in the cultrue after 5 hours? How long until there are 20,000 bacteria? Hmmm, what is "the law of unlimited growth"...

**Pre-Calculus**

The formula D= 5e ^-0.4h can be used to find the number of milligrams D of a certain drug that is in a patient's bloodstream h hours after the drug has been administered. When the number of milligrams reaches 2, the drug is to be administered again. WHat is the time ...

**Pre Calculs**

The pH of a chemical solution is given by the formula pH = -log10 [H+] where [H+] is the concentration of hydrogen ions in moles per liter. Values of pH range from 0 (acidic) to 14 (alkaline). (a) what is the pH of the solution for which [H+] is 0.1? (b) What happens to pH as ...

**Pre-Calculus**

The period T (in seconds) of a simple pendulum is a function of its length l (in feet), given by T(l) = 2pi sq root of l/g, where g = 32.2 feet per second per seconds is the acceleration of gravity. Express the length l as a function of the period T. If T=2pi*sqrt(l/g) then do...

**Pre-Calculus**

The function f(x)= x^4 is not one-to-one. Find a suitable restriction on the domain of f so that the new function that results is one-to-one. Then find the inverse of f. Restrict it to be non-negative to meet the 1-1 requirement.

**pre-calculus**

the spread of oil leaking from a tanker is in the shape of a circle. If the radius r (in feet) of the spread after t hours is r(t)= 200 square root of t, find the area A of the oil slick as a function of the time t. You know that the area of a circle is A=pi*r^2. You're ...

**Pre-Calculus**

The surface ares S (in square meters) of a hot air ballon is given by s(r)=4 pi r^2 where r is radius of balloon (in meters). If the radius r is increasing with time (in seconds) according to the formula r(t) = 2/3t^3, t is greater than or equal to 0, find the surface area S ...

**percentages**

20%

**Pre-Calculus**

The monthly revenue acheived by selling x boxes of candy is calculated to be x(5-0.05x)dollars. The wholesale cost of each box of candy is $1.50. How many boxes must be sold each month to achieve a profit of at least $60. Can someone please let me know how to set up this ...

**Math**

the answer is 70 because it is a multiple of both 2 and 7, it is less than 100 but larger then 50, and it is the product of 3 primes 2,5, and 7

**science**

One of the five charateristics of living things is being able to reproduce. Do all living things have to have all charateristics? Mules are living things and most are sterile. (I have heard of a few cases where a mule has given birth.) What about women who are sterile, they ...