Question

Solve the system by elimination.
x+5y-4z=-10
2x-y+5z=-9
2x-10y-5z=0

a.) (5, –1, 0)
b.) (–5, 1, 0)
c.) (–5, –1, 0)
d.) (–5, –1, –2)

Answer 1

@amorfide Helppp!):

Answer 2

@satellite73 ??

Answer 3

x+5y-4z=-10 equation 1
2x-y+5z=-9 equation 2
2x-10y-5z=0 equation 3

okay so you want to rearrange an equation
lets rearrange the first one and make x the subject

x+5y-4z=-10 equation 1


x=-10-5y+4z

now we want to substitute this into the other two equations we have
equation 2 and 3
2x-y+5z=-9 equation 2
2x-10y-5z=0 equation 3

these become

2(-10-5y+4z)-y+5z=-9 equation 2

2(-10-5y+4z)-10y-5z=0 equation 3

simplify these two get simultaneous equations with two unknowns

-20-10y+8z-y+5z=-9
-11y+13z=11 equation 2


-20-10y+8z-10y-5z=0
-20y+3z=20 equation 3

put these side by side

-11y+13z=11 equation 2
-20y+3z=20 equation 3


now rearrange one of these to get y the subject or z the subject

-11y=11-13z

y=(11-13z)/-11

substitute this into equation 3

-20(11-13z)/-11 + 3z=20

simplify

(-220+260z)/-11 +3z=20

multiply by -11 to get rid of the fraction

-220+260z -33z = -220
157z=0
z=0

now substitute z=0 into
-11y+13z=11 equation 2

-11y+13(0)=11

-11y=11
y=-1

substitute z=0 and y=-1 into original equation

x+5y-4z=-10 equation 1

x+5(-1)-4(0)=-10
x-5=-10
x=-5

just to make sure

substitute x=-5
y=-1
z=0

into the other two original equations

2x-y+5z=-9 equation 2

2(-5)-(-1)+5(0)=-9
-10+1=-9
-9=-9


2x-10y-5z=0

2(-5)-10(-1)-5(0)=0

-10+10=0
0=0


x=-5

y=-1

z=0

Answer 4

Thank you so much!!! Would you be able to help me with one more?

Answer 5

does this help/ does this make sense?

Answer 6

Solve the system by substitution.
2x-y+z=-4
z=5
-2x+3y-z=-10


a.) (-8, 7, 5)
b.) (–8, –7, 5)
c.) (8, –7, 5)
d.)(–8, –7, –5)

Answer 7

Can you help me with this one too? /:

Answer 8

you can do this...
you are given the value of Z
substitute it into the other 2 equations, then you will have two equations with two unknowns

then you will rearrange one of the equations to make y the subject or x the subject
lets say you make y the subject
substitute y into the other equation you have

then you will get a value for x
then substitute x into one of the two equations you have
to get y

Answer 9

Okk, let me try it. Then will you check my answers?

Answer 10

yes

Answer 11

Ok.... I'm confused..

Answer 12

confused with what