Problem 1:
x+y=-8
-3x+2y=9
Answers:
-5,-3
0,0
2,6
no solution
Problem 2:
y=x+5
x+y=9
Answers:
-5,0
2,7
4,5
no solution
2006-11-26 11:13:53 · 9 answers · asked by ginger b 1 in Science & Mathematics ➔ Mathematics
These two problems are examples of simultaneous linear equations in two unknowns.
solution for prob. 1:
x + y = -8 ---> eq.1
-3x + 2y = 9 ---> eq. 2
solve for x in eq.1
x = -8 - y ---> eq. 3
substiture eq. 3 in eq. 2
-3(-8 - y) + 2y = 9
24 + 3y + 2y = 9
24 + 5y = 9
solve for y
5y = 9 - 24
5y = -15
then y = -3 substitute this back in eq. 3 to solve for x: x = -8 - (-3)
x = -8 + 3
x = - 5
therefore the missing values for x and y are -5 and -3 respectively
solution for problem # 2:
y = x + 5 eq. 1
x + y = 9 eq. 2
subtitute eq. 1 in eq. 2
x + (x+5) = 9
2x + 5 = 9
2x = 9 -5
2x = 4
x = 2 substitute this back in eq. 1
y = 2 + 5
y = 7
the values for x and y are 2 and 7 respectively
hope this helps :-)
2006-11-26 11:32:43 · answer #1 · answered by Samara 2 · 0⤊ 1⤋
1) x+y = -8. So 3x + 3y = -24. Now add this equation to the second equation. So 3x - 3x + 3y+ 2y = -24 + 9. 5y = -15. y =-3. Now find x. x + -3 =-8. x = -5. The answer is (-5,-3)
2) y = x+5. So just substitute for y in the second equation. x+x+5 = 9. 2x+5 = 9. 2x = 4. x = 2. y = 2 +5. y = 7. The answer is (2,7)
2006-11-26 11:21:08 · answer #2 · answered by Edgar Greenberg 5 · 0⤊ 1⤋
(1) Multiply 1st equation by 3 and then add equations to get:
3x+ 3y=-24
-3x+ 2y= 9
----------------
5y=-15 or y=-3
Substitute original equation to get -3+ y=-8 or y=-5
(2) Rearrange 1st equation as -x+y=5. Then:
-x+y=5
x+y=9
----------
2y=14 or y=7
Substitute in 2nd equation to get x+7=9 or x=2
2006-11-26 11:42:40 · answer #3 · answered by Jimmy C 1 · 0⤊ 0⤋
You really shouldn't ask other people to do your homework for you. Multiple choice is super easy because you can plug the answers in and see if they work.
For example:
Does -5 + -3 equal -8? Just keep going from there. To do it the right way and actually solve the problem just substitue the first equation into the second by solving for one of the variables and replacing that in the other equation.
To solve the first one.
x + y = -8 so
x = -8 - y
You just put (-8 - y) into the second equation where x is
-3(-8 - y) + 2y = 9 and solve for y. You can then put this value into either of the equations and solve for x.
2006-11-26 11:24:33 · answer #4 · answered by Dan 2 · 0⤊ 1⤋
situation one million: x - y = 3 x + 2y = 6 Step 2 ----- 2x - 2y = 6 (multiplying finished line with the aid of 2) x + 2y = 6 ----------------- 3x = 12 (-2y and +2y get cancelled) So x = 12/3 = 4, if x is 4 fixing line one million we get y = one million (bcos x - y = 3) situation 2: x + y = 3 2x - 3y = 26 Step 2---- 3x + 3y = 9 (multiply finished line with the aid of 3) 2x - 3y = 26 ------------------ 5x = 35 So x = 35/5 = 7. If x is 7 then y = -4 (bcos x + y = 3) solutions could be confirmed with the aid of fixing any of the equations with the solutions.
2016-10-13 04:14:56 · answer #5 · answered by balick 4 · 0⤊ 0⤋
Problem 1:
(-5,-3) first, you have to plug in the solution into both problems and see if it works.
-5-3=-8 correct!
-3 * -5 + 2 * -3 = 9
15-6=9 correct!
Problem 2
(2,7)
7 = 2+5 correct!
2+7=9 correct!
2006-11-26 11:19:03 · answer #6 · answered by Peacock11 2 · 2⤊ 1⤋
In Problem 1, it's the first answer (-5,-3)
In Problem2, it's the second answer (2,7)
2006-11-26 11:19:14 · answer #7 · answered by Anonymous · 0⤊ 1⤋
these are simply "plug and chug" type questions. just substitute in the answers and see which ones work.
ANSWERS... D and B
2006-11-26 11:16:55 · answer #8 · answered by brandonlsmithe 2 · 0⤊ 2⤋
first question: -5,-3
second question: 2,7
2006-11-26 11:22:00 · answer #9 · answered by supersymmetry 1 · 0⤊ 1⤋