2x + 5y = -30 and 3x – 4y = 1 can you show how u got the anwser so i can learn
2006-10-11 03:57:33 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
2x + 5y = -30
3x - 4y = 1
Multiply first equation by 3 and second equation by -2 and adding the equations
6x + 15y = -90
-6x + 8y = -2
------------------
23y = - 92
y = - 92 / 23 = - 4
Substituting this in second equation
3x + 4 * 4 = 1
3x = 1 - 16
3x = - 15
x = - 15 / 3
x = - 5
Therefore solution is
x = - 5
and
y = - 4
2006-10-11 04:06:46 · answer #1 · answered by fsm 3 · 0⤊ 0⤋
2x +5y = -30. let this equation be eq. A
3x -4y = 1. let this be eq B.
Now to eliminate 'x' we multiply eq.A by 3 ( so 2x becomes 6x).
And eq.B by 2 ( So 3x becomes 6x. and hence can be cancelled)
the system becomes:
6x + 15y = -90
6x - 8y = 2
Now we subtract the equations,( remember to multiply each number on both sides),
On subtracting, 6x cancels and we have,
23y = - 92
=> y = -92/23.
So, y = -4.
Now we put this value in any equation and get value of of x,
3x - 4y = 1.
3x - (-4 *4) = 1
3x = 1 - 16
3x = -15
x = -15 / 3
x = -5.
Hope you get that.
:-)
2006-10-11 04:09:05 · answer #2 · answered by Anurag 2 · 1⤊ 0⤋
Line up all the elements like a subtraction problem.
Find a common demoniator for ONE of the variables... In this case X the Lowest Common Denominator is 6
So multiply the first equation by 3 and the second equation by 2
Subtract the two equations from each other and you are left with:
15y+8y=-90-3
23y=-93
Divide by 23 and you have your solution
2006-10-11 04:03:28 · answer #3 · answered by klilly84 2 · 0⤊ 0⤋
2x+5y= -30 *3(multiply eqn)
3x-4y= 1 *2
= 6x+15y= -90
6x- 8y= 2
on subtracting
23y= -92
y= -4
in eqn 1 then,
2x+5(-4)=-30
2x-20=-30
2x=-10
x =-5
2006-10-11 04:04:57 · answer #4 · answered by book lover 1 · 0⤊ 0⤋
Multiply the first equation by 4 and the second equation by 5. Once you have done that stack up the equations and add them together to eliminate one of the variables.
Once you have a value for one of the variables, substitute that value in for the variable in one of the original equations.
Hope this helps. Good Luck.
2006-10-11 04:02:59 · answer #5 · answered by SmileyGirl 4 · 0⤊ 0⤋
is this ur home work?
giving all the questions of same type
ok let me help u
multiply 1st eq with 3 & 2nd eq with 2
we get
6x+15y=-90
6x - 8y = 1 by substracting we get
______________
23y=-91
y=-91/23
then find x
2006-10-11 03:59:54 · answer #6 · answered by . 3 · 0⤊ 0⤋
i think that x=125/23 and y=88/23.
2006-10-11 07:18:04 · answer #7 · answered by Roxy 2 · 0⤊ 0⤋