-2x-3y= 7
更新1:
x+5y= -7 -2x - 3y= 7 x= y=
solve the system of equations?
回答 (6)
2009-03-09 9:47 am
✔ 最佳答案
Solve it using substitution methodLet x+5y=-7 ----Equation 1
Arrange equation in x= -7-5y
Let -2x-3y = 7-----Equation 2
Substitute equation 1 into 2
-2(-7-5y)-3y =7
14+10y-3y = 7
7y = -7
y=-1
When y=-1 substitute into equation 1 to find x
x= -7-5(-1)
=-2
2009-03-09 9:47 am
2*(x+5y)=2*(-7) Multiply the equation by two and you will get...
2x+10y=-14 ...this equation...
-2x-3y=7 ...with this second equation, the x's will now fall out when you add the two equations together...
7y=-7 ...solve for y and you get...
y=-1
x+5*(-1)=-7 ...substitute the -1 back into any of the equations for y and solve for x...
x-5=-7 ...simplify to get...
x=-2
2x+10y=-14 ...this equation...
-2x-3y=7 ...with this second equation, the x's will now fall out when you add the two equations together...
7y=-7 ...solve for y and you get...
y=-1
x+5*(-1)=-7 ...substitute the -1 back into any of the equations for y and solve for x...
x-5=-7 ...simplify to get...
x=-2
2009-03-09 11:26 am
x + 5y = -7 (solve by using elimination)
-2x - 3y = 7
x + 5y = -7
-2(x + 5y) = -2(-7)
-2x - 10y = 14
...-2x - 10y = 14
–) -2x - 3y = 7 (subtraction)
---------------------------------
-7y = 7
-7y = 7
y = 7/-7
y = -1
x + 5y = -7
x + 5(-1) = -7
x + (-5) = -7
x = -7 + 5
x = -2
â´ x = -2 , y = -1
-2x - 3y = 7
x + 5y = -7
-2(x + 5y) = -2(-7)
-2x - 10y = 14
...-2x - 10y = 14
–) -2x - 3y = 7 (subtraction)
---------------------------------
-7y = 7
-7y = 7
y = 7/-7
y = -1
x + 5y = -7
x + 5(-1) = -7
x + (-5) = -7
x = -7 + 5
x = -2
â´ x = -2 , y = -1
2009-03-09 10:04 am
x+ 5y= -7
-2x-3y=7
-2x-39-1/5x-7)=7
-2x+3/5x+21=7
-10/5x+ 3/5x= -14
-7/5x= -14
(-5/7) -7/5x= -14 (-5/7)
x= 70/7
x= 10
plug 10 into equation where you see x
when 10 is plugged into x+ 5y= 7 the equation becomes
10+5y= -7
subtract 10 from both sides
5y= -7-10
5y= -17
divide each side by 5
y= -17/5
-2x-3y=7
-2x-39-1/5x-7)=7
-2x+3/5x+21=7
-10/5x+ 3/5x= -14
-7/5x= -14
(-5/7) -7/5x= -14 (-5/7)
x= 70/7
x= 10
plug 10 into equation where you see x
when 10 is plugged into x+ 5y= 7 the equation becomes
10+5y= -7
subtract 10 from both sides
5y= -7-10
5y= -17
divide each side by 5
y= -17/5
2009-03-09 9:55 am
x+5y=-7
-2x-3y=7
x+5y=-7
x=-7-5y
sub. x=-7-5y in equation 2
-2(-7-5y) -3y=7 [expand]
14+10y-3y=7[like terms + balance]
7y=-7 [make y the subject]
therefore y=-1
x+5y=-7
x+5(-1)=-7
x-5=-7
therefore x=-2
x=-2
y=-1
edit: omg there were no answers just a second ago, dammit should had submitted earlier
-2x-3y=7
x+5y=-7
x=-7-5y
sub. x=-7-5y in equation 2
-2(-7-5y) -3y=7 [expand]
14+10y-3y=7[like terms + balance]
7y=-7 [make y the subject]
therefore y=-1
x+5y=-7
x+5(-1)=-7
x-5=-7
therefore x=-2
x=-2
y=-1
edit: omg there were no answers just a second ago, dammit should had submitted earlier
參考: mmeeee
2009-03-09 9:54 am
x+5y=-7
x= -7-5y (1)
you put that value of x in the equation -2x-3y=7
-2*(-7-5y)-3y =7
14+7y = 7
7y =7-14=-7
y=-1 (put that value in (1)
x= -7-5*-1=7-2
so result x= -1 y= -2
x= -7-5y (1)
you put that value of x in the equation -2x-3y=7
-2*(-7-5y)-3y =7
14+7y = 7
7y =7-14=-7
y=-1 (put that value in (1)
x= -7-5*-1=7-2
so result x= -1 y= -2
收錄日期: 2021-05-01 12:09:48
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