can someone help me with simultaneous equations by substitution? (1 Viewer)

[kaha167]

i need help with the following:

1. y = x^2
y = x

2. y = x^2
2x + y = 0

3. x^2 + y^2 = 9
x + y = 3

thanks so much for the help

 

[GUSSSSSSSSSSSSS]

y=x and y=x^2
x = x^2
x^2 - x = 0
x(1 - x) = 0
x = 0,1


sorry i cbb to do the others, but just make y the subject and sub it in, factorise and make equal to zero

good luck XDDD

 

[iSplicer]

i need help with the following:

1. y = x^2
y = x

2. y = x^2
2x + y = 0

3. x^2 + y^2 = 9
x + y = 3

thanks so much for the help

This is fairly basic maths...


1. sub y into the other equation:
x^2 = x, solve for the two values of x, sub these back in, and get your two values for y.

2. make Y the subject for the second equation, then just sub y into the other equation:
-2x = x^2 solve for the two values of x, sub these back in, and get your two values for y.

3. Just make y the subject in the linear equation (y = 3-x) and sub this into the other equation:

x^2 + (3-x)^2 = 9 Yet again, solve for the two values of x, sub these back in, and get your two values for y.

Hope that helped =)

 

[TheFeared]

Actually for 2 iSplicer
2x+x^2=0
x(2+x)=0
x= 0 & -2

 

[Aquawhite]

This should have been posted in the Maths threads of the forums...

 

[iRuler]

^ nah, well I think you should only post in the maths sections if it's year 12 (HSC) maths?

 

[duckcowhybrid]

3.

x^2 + y^2 = 9 - Eqn 1
x + y = 3 - Eqn 2

From Eqn 2

y = 3-x

Substituing this into Eqn 1, we get:

x^2 + (3-x)^2= 9

x^2 + 9 - 6x + x^2 = 9

2x^2 - 6x = 0

x^2 + 3x = 0

x(x+3) = 0

x = 0 or -3

Sorry for the long and boring working out I wrote out every line. Basic algebra really.