MathS!!!!!!!!!!!!!?

þяiηcεss ηo 1: MathS!!!!!!!!!!!!!?
4(x-2y)-(5x+3y)=30
3(3x+7y)-2(x+9y)=12

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Answers and Views:

Answer by Skefizy
simplifies to

-x – 11 y = 30
7 x + 3 y = 12

Fill in the first equation in the second (x=-11y – 30). You get {x = 3, y = -3}

Answer by Moise Gunen
compute (

4x-8y -5x-3y=30
9x+21y-2x-18y=12

-x-11y=30
7x+3y=12

-7x-77y=210
7x+3y=12

add
-74y=222
y=-3
x=-11y-30=3

Answer by Makes Me Wonder
4(x-2y)- (5x+3y)= 30
3(3x+7y)- 2(x+9y)= 12

4(x-2y)- (5x+3y)= 30
4x – 8y – 5x -3y= 30
-x -11y= 30 [1]

3(3x+7y)- 2(x+9y)= 12
9x +21y -2x -18y= 12
7x +3y= 12 [2]

simultaneous equations:
-x -11y =30 [1]
7x +3y= 12 [2]

rearrange eqn. [1]
x +11y= -30
x= -30- 11y

sub. x= -30 -11y
7(-30 -11y) +3y= 12
-210 -77y +3y= 12
-74y= 222
y= -3

sub. y= -3 in eqn. [2]
7x +3y =12
7x +3(-3)= 12
7x -9= 12
7x= 21
x =3

ANSWER: x= 3, y= -3

Answer by sun devill
first equation:

4(x-2y)-(5x+3y)=30 distribute
4x -8y -5x-3y =30 simplify
-1x-11y=30

second equation:

3(3x+7y)-2(x+9y)=12
9x+21y -2x-18y=12
7x+3y=12

then your going to have to take the two simplified equations and do linear combination or substitution

7x+3y=12
-1x-11y=30
multiply bottom equation by 7 (all of it)
-7x-77y=210
7x+3y=12
add them and the x’s cancel
80y=222
y=2.775
then plug it back into another equation and solve
sorry it might be wrong
have to go somewhere

Answer by Yaton_123
first start off by expanding if out of the brackets
4x – 8y – 5x – 3y = 30
9x + 21y – 2x – 18y = 12

then u collect like terms
4x – 5x – 8y – 3y = 30
9x – 2x + 21y -18y = 12

simplify
-x – 11y = 30
7x + 3y = 12

isolate for an variable
-x -11y = 30
—–> x = -11y – 30

now sub this x value into the second equation
7( -11y – 30) + 3y = 12
—–> -77y – 210 + 3y = 12
—–> -74y = 222

solve
y = -3

plot y into the x value
x = -11(-3) – 30
—–>x = 33 – 30
—–>x = 3

answer : x = 3, y = -3

Answer by hobbyist
Hi, look carefully:
4x-8y-5x-3y=30,
9x+21y-2x-18y=12

(4x-5x)+(-8y-3y)=30,
(9x-2x)+(21y-18y)=12

-x-11y=30,
7x+3y=12

-30-11y=x,
7x+3y=12

-30-11y=x,
7(-30-11y)+3y=12

-30-11y=x,
-210-77y+3y=12

-30-11y=x,
-210-74y=12

-30-11y=x,
-210-12=74y

-30-11y=x,
-222=74y

-30-11y=x,
-3=y

-30-11*(-3)=x,
-3=y

-30+33=x,
-3=y

3=x,
-3=y

Answer by dasnaamic
Expand the brackets:
4x-8y-5x-3y=30 > -x-11y=30
9x+21y-2x-18y=12 > 7x+3y=12

Now you have 2 simultaneous equations:
-x-11y=30 – Number 1
7x+3y=12 – Number 2

allow number 1 to make x the subject of the formula:
x= -11y-30 – Number 1

substitute this into equation number 2:
7(-11y-30)+3y=12
-77y-210+3y=12

-74y=222
y=222/-74

y=-3

Now that y is -3, look at equation number 1:
-x-11y=30

becuase y is -3, you can change y into -3:
-x-(11*-3)=30
-x+33=30
-x=-3
x=3

therefore, y is -3
x is 3