Posted by **hiroko** on Saturday, November 9, 2013 at 5:36am.

Find all rational zeros of the function. Then (if necessary) use the depressed equation to find all roots of the equation f(x)=0

f(x)= 5x^4-11x^3-33x^2+77x-14

- math -
**Reiny**, Saturday, November 9, 2013 at 8:50am
trying x = ±1, ±2, ± 7, ±1/5, ±2/5, ±7/5

I found f(2) = 0

and f(x) = (x-2)(5x^3 - x^2 - 35x + 7) = (x-2)g(x)

x = ±7 didn't work in the first, so it certainly will not work in this one

so try x = 1/5 in the cubic factor

g(1/5) = 5(1/125) - 1/25 - 35(1/5) + 7 = 0

so we have

f(x) = (x-2)(5x-1)(x^2 - 7) after a division

roots are

x = 2, 1/5, ± √7

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