simultaneous equations

i know the answers, i'm sure i know how to work it out but i never get the right answer, so if someone can show me their working out that'd be great, need to know urgently, revising for a test tomorrow.

solve the simultaneous equations
a) 2x+y=4
x^2+2y^2=17

Reply 1

aznkid66

1

Substitution is your friend.

After all, if you can't solve a quadratic in two variables, then solve a quadratic in one! :P

(edited 11 years ago)

Reply 2

TenOfThem

18

Original post by dippers

i know the answers, i'm sure i know how to work it out but i never get the right answer, so if someone can show me their working out that'd be great, need to know urgently, revising for a test tomorrow.

solve the simultaneous equations
a) 2x+y=4
x^2+2y^2=17

What have you used as your starting point

--

Original post by dippers

i know the answers, i'm sure i know how to work it out but i never get the right answer, so if someone can show me their working out that'd be great, need to know urgently, revising for a test tomorrow.

solve the simultaneous equations
a) 2x+y=4
x^2+2y^2=17

Set the y in the first equation as the subject so you get y=4-2x

Substitute this into the second equation, so wherever you have y put in (4-2x).

By doing this you get an equation with one unknown which is easier to solve.

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Reply 5

Artemis 97

11

rearrange the linear and substitute into the quadratic would be easiest. You could also square the liner (once rearranged) and solve simultaneously if you prefer.

Spoiler

(edited 11 years ago)

simultaneous equations

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