Does x + y = 5 ?
(1) 4x + y = 17
(2) x + 4y = 8
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wait, how is (1) alone not enough? I plugged in and got a value for x+y... am I missing something?
you can't find x+y from just one equation with two variables, you'd need another relation. Try picking different x values and you'll see y changes too
once you realize neither alone pins down x+y, combining the two is straightforward. pretty quick one.
yep, two equations two variables, done. classic C trap if you rush though
Easy but I almost picked D because both look sufficient individually at first glance 😅
same lol, they look symmetric which makes you think each works alone
thanks, this one clicked fast. good confidence booster before the harder sets.
What it tests
Your ability to manipulate linear and quadratic expressions, substitute unknowns, and solve equations under time pressure.
Common trap
Losing a sign when moving terms across the equals sign, or dividing both sides by a variable that could equal zero.