Math Is Fun Forum

2x - 3y=-6
am I right in thinking that it would be f(x) = 3/2x-6

coffee beans sell for $9 per pd and $12 pe4r pd; the 2 are mixed to create 100 pds that sell for $11.25 per pd;
how much of each type will be used?

x(beans sold @$9 pd) + y(beans sold @$12 pd)=100
9(12y+100)+12y=1125
108y+900+12y=1125
120y+900=1125
120y=1125-900
120y=225
What am I missing???
x=25 pds, y=75 pds

I am having trouble with this:  it is to be solved by subsitition 4x-12y=5; -x+3y=-1

4(-3y + 1) -12 y = 5; -12y +4 -12y =5;  24y +4 =5  24y= -4+5; 24y=1 y=1/24 am I doing this right??

have $3.50 in nickels and dimes; total 50 coins how many of each

n + d =50                 
5n + 10d = 350                                       
5 d = 35
d= -5 + 35=30
n + 30 = 50
n=20

20 + 30 = 50

5(20) + 10(30)= 100 +  300 = $4.00
what do I have to change to get $3.50? they should have been just the opposite

solve each of the following systems of linear inequalities graphically
3x-y<=6 ; x>=1 ; y<=3  if you do 3x - 0 =6 then 3x=6 and x<=2; and 3(1) - y(-3) =6 3+3=6; so you would graph (2,0) and (1,-3) but then on x>=1 you would put that at 1 on the x axis; and for y<=3 you would put that on the 3 of the y axis. is that the correct way to solve this problem??

length of a rectangle is 2 inches mor than twice its width. if the perimeter of the rectangle is 34 inches find the demensiions of the rectangle; 2(length +width) =34; 2(2+2x)+x=34; 4+6x=34;6x=30; x=5 if that is right I am now beside myself in other words I am lost as to how to find the solution

solve systems by addition
x+5y=10 and -2x -10y=-20 so if multiply the first equation by 2 I get 2x+10y=20 to me that would cancel out the other equation I'm so lost????

2x+3y=1 and 5x+3y=16 state whether incon sistent or dependent; if I multiply the first equation by -1, Iget -2x-3y=-1 which means x=5 but then when I plug that into 5(5) +3y=16; 25+3y=16; 3y=-25+16; 3y=9;y=3   2(5) +3(3) =1 10 +9=1?   5(5) +3(3)=16 25+9=16 what am I doing wrong?

An inventor of a new product believes that the cost of producing the product is given by the function C(x) = 1.75x + 7000.

If the inventor charges $4 per unit, then her profit for producing and selling x units is given by the function P(x) = 2.25x - 7000

a) What is her profit if she sells 2000 units?
b) What is her profit if she sells 5000 units?
c) What is the break-even point for sales?

How do I work a,b, and c?