SOLUTION: Use the quadratic formula to solve 2y^2 - 6y - 8 = 0

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Question 189841: Use the quadratic formula to solve 2y^2 - 6y - 8 = 0
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

2y%5E2-6y-8=0 Start with the given equation.


Notice we have a quadratic equation in the form of ay%5E2%2Bby%2Bc where a=2, b=-6, and c=-8


Let's use the quadratic formula to solve for y


y+=+%28-b+%2B-+sqrt%28+b%5E2-4ac+%29%29%2F%282a%29 Start with the quadratic formula


y+=+%28-%28-6%29+%2B-+sqrt%28+%28-6%29%5E2-4%282%29%28-8%29+%29%29%2F%282%282%29%29 Plug in a=2, b=-6, and c=-8


y+=+%286+%2B-+sqrt%28+%28-6%29%5E2-4%282%29%28-8%29+%29%29%2F%282%282%29%29 Negate -6 to get 6.


y+=+%286+%2B-+sqrt%28+36-4%282%29%28-8%29+%29%29%2F%282%282%29%29 Square -6 to get 36.


y+=+%286+%2B-+sqrt%28+36--64+%29%29%2F%282%282%29%29 Multiply 4%282%29%28-8%29 to get -64


y+=+%286+%2B-+sqrt%28+36%2B64+%29%29%2F%282%282%29%29 Rewrite sqrt%2836--64%29 as sqrt%2836%2B64%29


y+=+%286+%2B-+sqrt%28+100+%29%29%2F%282%282%29%29 Add 36 to 64 to get 100


y+=+%286+%2B-+sqrt%28+100+%29%29%2F%284%29 Multiply 2 and 2 to get 4.


y+=+%286+%2B-+10%29%2F%284%29 Take the square root of 100 to get 10.


y+=+%286+%2B+10%29%2F%284%29 or y+=+%286+-+10%29%2F%284%29 Break up the expression.


y+=+%2816%29%2F%284%29 or y+=++%28-4%29%2F%284%29 Combine like terms.


y+=+4 or y+=+-1 Simplify.


So the answers are y+=+4 or y+=+-1