SOLUTION: If the ellipse defined by the equation 16x^2+4y^2+96x-8y+84=0 is translated 6 units down and 7 units to the left, write the standard equation of the resulting ellipse

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Question 625240: If the ellipse defined by the equation 16x^2+4y^2+96x-8y+84=0 is translated 6 units down and 7 units to the left, write the standard equation of the resulting ellipse
Answer by Edwin McCravy(20060)   (Show Source): You can put this solution on YOUR website!
16x² + 4y² + 96x - 8y + 84 = 0

Get the constant term off the left side by adding -84 to both sides

   16x² + 96x + 4y² - 8y = -84

Swap the two middle terms

   16x² + 96x + 4y² - 8y = -84

Factor out the coefficients of x² and y² 

16(x² + 6x) + 4(y² - 2y) = -84

To complete the square inside the first parenhtheses,
1. Multiply the coefficient of x, which is +6 by 1/2, getting 3
2. Square this result, (3)² = +9
3. Add +9 inside the first parentheses
4. Multiply +9 by the coefficient we factored out, 16, getting +144
5. Add +144 to the right side  

16(x² + 6x + 9) + 4(y² - 2y) = -84 + 144

To complete the square inside the second parenhtheses,
1. Multiply the coefficient of y, which is -2 by 1/2, getting -1
2. Square this result, (-1)² = +1
3. Add +9 inside the first parentheses
4. Multiply +1 by the coefficient we factored out, 4, getting +4
5. Add +4 to the right side  

16(x² + 6x + 9) + 4(y² - 2y + 1) = -84 + 144 + 4

Factor the 1st parentheses:  x² + 6x + 9 = (x + 3)(x + 3) = (x + 3)²
Factor the 2nd parentheses:  y² - 2x + 1 = (y - 1)(y - 1) = (y - 1)²
Combine terms on the right:  -84 + 144 + 4 = 64

16(x + 3)² + 4(y - 1)² = 64

Get a 1 on the right side by dividing through by 64

 +  = 

 +  = 1

 +  = 1

To translate this equation 6 units down and 7 units to the left,
replace y by (y+6) and x by (x+7)

 +  = 1

 +  = 1

 +  = 1

Edwin

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