`x+y=-6`
`y-4x=4`
If the ordered pair (x, y) satisfies the system of equations shown above, what is the value of xy?

Explanation

Difficult: Medium
Category: Heart of Algebra/ System of Linear Equations
Strategic Advice: When answering a Grib-in question, it is particully important to check that you answered the right question before you grid in your answer.
Getting to the Answer: Use substitution or combination (elimination) to find the solution to the system. If you choose combination, the second equation needs to be rearranged so that like terms are linked up vertically, and you'll need to multiply the first equation by 4 so that the x terms are eliminated when you add the equations
`4[x+y-6] to 4x+4y=24`
`y-4x=4 to (##KPL_SAT_MAT_PRP_PS_02_E01_001_S01.png" width="80%">
`y=-4`
From the first equation, `x+y=-6` gives `x+(-4)=-6`, so `x=-2`. The question asks for the value of xy, multiply to get `(-2)times(-4)=8`.