SOLUTION: Select the approximate values of x that are solutions to f(x) = 0, where f(x) = -5x2 + 9x + 3. possible answers please help {–1.67, 3.00} {-5, 9} {–1.80, –0.60}

Algebra ->  Graphs -> SOLUTION: Select the approximate values of x that are solutions to f(x) = 0, where f(x) = -5x2 + 9x + 3. possible answers please help {–1.67, 3.00} {-5, 9} {–1.80, –0.60}       Log On


   

Question 882137:
Select the approximate values of x that are solutions to f(x) = 0, where
f(x) = -5x2 + 9x + 3.
possible answers please help
{–1.67, 3.00}
{-5, 9}
{–1.80, –0.60}
{–0.29, 2.09}
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
x=%28-9%2B-+sqrt%2881-4%2A%28-5%293%29%29%2F%28-10%29
x=%28-9%2B-+sqrt%2881%2B60%29%29%2F%28-10%29
x=%28-9%2B-+sqrt%28141%29%29%2F-10
x=%289%2B-+sqrt%28141%29%29%2F10, 141=3*47
x=%289%2B-+11.874%29%2F10

Examining your four choices and comparing to your expression for x, you must have exactly one positive solution and one negative solution. Your added form is positive and your subtraction form is negative. You can eliminate choice 3. The added form is estimable to be about (10+10)/10=2, approximately. This suggests choice number neither choice 1 nor 2.
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The subtraction form? approx. -2/10=-1/5. This looks like choice 4 is the closest choice. {-0.29, 2.09}.

Finish computing x. {-0.2874, 2.0874}.