x + y + z = 100
x - z = 45
2z^2 + 40 = 90
2007-09-04 01:27:47 · 11 answers · asked by Axis Flip 3 in Science & Mathematics ➔ Mathematics
Find the variable y.
2007-09-04 01:28:08 · update #1
The answer given by bill-e is good but he has made a mistake.
He has taken z=+5 while evaluating y. He forgot to take z=-5. He has taken z=+/- 5 only upto the evaluation of the value of x. x=50 when z=5 and it is = 40 when z=-5.
So 50+y+5=100 gives y = 45
and 40+y-5=100 gives y = 65
2007-09-04 01:54:31 · answer #1 · answered by Indian Primrose 6 · 0⤊ 0⤋
I get
y = 45
2z^2 + 40 = 90 (z=5)
x - z = 45 (x = 45 +5 = 50)
x + y + z = 100 (y = 100 - 50 - 5)
2007-09-04 01:39:18 · answer #2 · answered by Dan 2 · 0⤊ 0⤋
thats easy...
from third equation,
2z^2 + 40 = 90,
2z^2 =90 - 40 = 50
therefore, z^2 = 25
or z = 5 or (-5) --------------(1)
now, from second equation,
x - z = 45,
, now since we have 2 values for z, we would get 2 values of x,
=> x - 5 = 45, or x - (-5) = 45,
=> x = 45 + 5, or x = 45 - 5,
=> x = 50, or x = 40,
therefore, the first eqn implys,
x + y + z = 100,
50 + y + 5 = 100 or 40 + y + (-5) = 100
y = 100 - 55 or y = 100 - 35
therefore, y = 45, or y = 65
2007-09-04 01:35:10 · answer #3 · answered by raja 2 · 0⤊ 0⤋
2z^2 + 40 = 90
2z^2 = 50
z^2 = 25
z = +5 or -5
x - 5 = 45 or x + 5 = 45
x = 50 or x = 40
50 + y + 5 = 100 or 40 + y + 5 = 100
y = 45 or y = 55
2007-09-04 01:41:44 · answer #4 · answered by ? 2 · 1⤊ 0⤋
95 + 5 = 100
50 + 40=90
2007-09-04 02:08:56 · answer #5 · answered by Anonymous · 1⤊ 0⤋
I too get 45
x-z=45
2z^2+40=90
2z^2= 90-40=50
z^2=25
z=5
x=45+5=50
y=100-50-5=45
2007-09-04 01:45:07 · answer #6 · answered by lux 2 · 0⤊ 0⤋
You'll have to work with all 3 equations to solve for the variable you're asked to find, this case 'y'. From what I see, the last equation you listed is the best one to begin with. Why? Because there is only one variable (z), so you'll be able to find z. After you find z, we look at the other 2 equations. You can't use the first one because we don't know 2 of the variables (x and y) making it impossible to solve, but the second one we only need to find one variable (x), so we now find x. Now you should know what 'x' and 'z' are, so you use thee first equation and solve for 'y'. Sorry for all the reading =)
2007-09-04 01:37:44 · answer #7 · answered by Anonymous · 0⤊ 0⤋
2z^2 + 40 = 90
2z^2 = 50
z^2 = 25
z = 5
x - 5 = 45
x = 50
50 + y + 5 = 100
y = 45
2007-09-04 01:34:34 · answer #8 · answered by Beardo 7 · 0⤊ 0⤋
if z = -5, then
x = 40 and
y = 965.
if z = 5, then
x = 50 and
y = 945.
that's my answer...
2007-09-04 01:45:06 · answer #9 · answered by Jocel B. Bartolay 2 · 0⤊ 0⤋
Don't waste my time with something this simple.
Solve the last equation to get z.
Sub that value into the second to get x
Sub x and z into the first to get y
As for the actual algebra, you'll never learn if I do it for you.
2007-09-04 01:49:23 · answer #10 · answered by tgypoi 5 · 0⤊ 0⤋