5x-y=9
x-1.5y=-3
i dont even kno what it means by elimination. i know how to solve by substitution, but not elimination....
Crazily enough, it's not ..... Elimination and substitution are taught as two seperate methods.
One way of applying the elimination method:
$\displaystyle 5x - y = 9$ .... (1)
$\displaystyle x - 1.5y = -3$ .... (2)
Multiply equation (2) by -5:
$\displaystyle -5x + 7.5y = 15$ .... (3)
Now add equation (1) and equation (3) to eliminate $\displaystyle x$:
$\displaystyle 6.5 y = 24 \Rightarrow y = \, ....$
Now substitute the value of $\displaystyle y$ into any equation and solve for $\displaystyle x$.
This is what is taught in schools (so don't shoot me ....)
What 3? I have labelled the equations (1), (2) and (3).
You add so that x gets eliminated.
I have (reasonably) assumed that you have some familiarity with the method ....
Read this: Systems of Linear Equations: Solving by Addition / Elimination