SOLUTION: 2x^2+3xy-4y^2 when x=2 and y=-4

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Question 252911: 2x^2+3xy-4y^2 when x=2 and y=-4
Found 2 solutions by jim_thompson5910, drk:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
2x%5E2%2B3xy-4y%5E2 Start with the given expression.


2%282%29%5E2%2B3%282%29%28-4%29-4%28-4%29%5E2 Plug in x=2 and y=-4


2%284%29%2B3%282%29%28-4%29-4%2816%29 Square 2 to get 4 and square -4 to get 16


8-24-64 Multiply


-80 Combine like terms.


So 2x%5E2%2B3xy-4y%5E2=-80 when x=2 and y=-4

Answer by drk(1908) About Me  (Show Source):
You can put this solution on YOUR website!
Here is the original equation:
2x%5E2+%2B+3xy+-+4y%5E2
Let: x = 2 and y = -4
--
step 1: replace x with 2 and y with -4 to get
2%2A%282%29%5E2%2B3%282%29%28-4%29-4%2A%28-4%29%5E2
use order of operations to simplify:
2%2A4+%2B+3%28-8%29+-+4%2816%29
8+-+24+-+64
-16+-+64
-80