SOLUTION: 9x^2+21x-8=0 i can have fractions for an answer

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Question 263253: 9x^2+21x-8=0 i can have fractions for an answer
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

9x%5E2%2B21x-8=0 Start with the given equation.


Notice that the quadratic 9x%5E2%2B21x-8 is in the form of Ax%5E2%2BBx%2BC where A=9, B=21, and C=-8


Let's use the quadratic formula to solve for "x":


x+=+%28-B+%2B-+sqrt%28+B%5E2-4AC+%29%29%2F%282A%29 Start with the quadratic formula


x+=+%28-%2821%29+%2B-+sqrt%28+%2821%29%5E2-4%289%29%28-8%29+%29%29%2F%282%289%29%29 Plug in A=9, B=21, and C=-8


x+=+%28-21+%2B-+sqrt%28+441-4%289%29%28-8%29+%29%29%2F%282%289%29%29 Square 21 to get 441.


x+=+%28-21+%2B-+sqrt%28+441--288+%29%29%2F%282%289%29%29 Multiply 4%289%29%28-8%29 to get -288


x+=+%28-21+%2B-+sqrt%28+441%2B288+%29%29%2F%282%289%29%29 Rewrite sqrt%28441--288%29 as sqrt%28441%2B288%29


x+=+%28-21+%2B-+sqrt%28+729+%29%29%2F%282%289%29%29 Add 441 to 288 to get 729


x+=+%28-21+%2B-+sqrt%28+729+%29%29%2F%2818%29 Multiply 2 and 9 to get 18.


x+=+%28-21+%2B-+27%29%2F%2818%29 Take the square root of 729 to get 27.


x+=+%28-21+%2B+27%29%2F%2818%29 or x+=+%28-21+-+27%29%2F%2818%29 Break up the expression.


x+=+%286%29%2F%2818%29 or x+=++%28-48%29%2F%2818%29 Combine like terms.


x+=+1%2F3 or x+=+-8%2F3 Simplify.


So the solutions are x+=+1%2F3 or x+=+-8%2F3