Spring 2018 | Professor Kate Poirier

# Month: May 2018(Page 1 of 5)

Read the instructions for the extra credit assignment here.

The new deadline for submitting your entry is 10am Thursday, May 24.

Voting is open now, though new memes may be added between now and Thursday. You may submit only one vote. Enter your vote here by 10pm Thursday, May 24. #7.

a) 3x + y = 4

x² – 3y = -32

First:

3x + y = 4

y = -3x + 4

Then:

x² – 3y = -32

x² – 3(-3x + 4) = -32

x² + 9x – 12 = -32

x² + 9x + 20 = 0

(x + 5) (x + 4) = 0

x + 5 = 0

x = -5

x + 4 = 0

x = -4

x = -5 AND x = -4

Next:

x² – 3y = -32

y = -3x + 4

y = -3(-5) + 4

y = 15 + 4

y = 19

y = -3x + 4

y = -3(-4) + 4

y = 12 + 4

y = 16

So:

(-5 , 19) ✓ AND (-4 , 16) ✓

Check:

3x + y = 4

x² – 3y = -32

3(-4) + 16 = 4

(-4)² – 3(16) = -32

-12 + 16 = 4

16 – 48 = -32

4 = 4 ✓

-32 = -32 ✓

(-4 , 16) ✓

AND

3x + y = 4

x² – 3y = -32

3(-5) + 19 = 4

(-5)² – 3(19) = -32

-15 + 19 = 4

25 – 57 = -32

4 = 4 ✓

-32 = -32 ✓

(-5 , 19) ✓

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