algebra

Select the approximate values of x that are solutions to f(x)=0, where f(x) = -2x^2+8x+5

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  1. so
    -2x^2 + 8x + 5 = 0
    x^2 - 4x = 5/2
    complete the square ...
    x^2 - 4x + 4 = 5/2 + 4
    (x-2)^2 = 13/2 = 26/4
    x-2 = √26/4 ........ since √26 is close to 5
    x = appr 2 ± 5/2
    = appr 4.5 or .5

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    posted by Reiny

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