SOLUTION: How do yu solve this by using quadratic formula 2 = 0.7n + 0.6n2? please show steps.

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Question 149485: How do yu solve this by using quadratic formula 2 = 0.7n + 0.6n2?
please show steps.
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
2+=+0.7n+%2B+0.6n%5E2 Start with the given equation.


10%282%29+=10%280.7n+%2B+0.6n%5E2%29 Multiply both sides by 10 to clear the decimals.


20+=7n+%2B+6n%5E2 Distribute and multiply.


0=7n+%2B+6n%5E2-20 Subtract 20 from both sides.


0=6n%5E2%2B7n-20 Subtract 20 from both sides.

Let's use the quadratic formula to solve for n


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


n+=+%28-%287%29+%2B-+sqrt%28+%287%29%5E2-4%286%29%28-20%29+%29%29%2F%282%286%29%29 Plug in a=6, b=7, and c=-20


n+=+%28-7+%2B-+sqrt%28+49-4%286%29%28-20%29+%29%29%2F%282%286%29%29 Square 7 to get 49.


n+=+%28-7+%2B-+sqrt%28+49--480+%29%29%2F%282%286%29%29 Multiply 4%286%29%28-20%29 to get -480


n+=+%28-7+%2B-+sqrt%28+49%2B480+%29%29%2F%282%286%29%29 Rewrite sqrt%2849--480%29 as sqrt%2849%2B480%29


n+=+%28-7+%2B-+sqrt%28+529+%29%29%2F%282%286%29%29 Add 49 to 480 to get 529


n+=+%28-7+%2B-+sqrt%28+529+%29%29%2F%2812%29 Multiply 2 and 6 to get 12.


n+=+%28-7+%2B-+23%29%2F%2812%29 Take the square root of 529 to get 23.


n+=+%28-7+%2B+23%29%2F%2812%29 or n+=+%28-7+-+23%29%2F%2812%29 Break up the expression.


n+=+%2816%29%2F%2812%29 or n+=++%28-30%29%2F%2812%29 Combine like terms.


n+=+4%2F3 or n+=+-5%2F2 Simplify.


So the answers are n+=+4%2F3 or n+=+-5%2F2 (which are approximately n+=+1.333 or n+=+-2.5)