Question

According to the Rational Root Theorem, Negative two-fifths is a potential rational root of which function?

Answer 1

Answer:

Neither expression satisfies the given rational root.

Step-by-step explanation:

To find the right answer, we just need to replace the given root in each expression and see which one gives zero.

First expression.

$f(x)=4x^{4} -7x^{2} +x+25\\f(-\frac{2}{5})= 4(-\frac{2}{5})^{4} -7(-\frac{2}{5})^{2} +(-\frac{2}{5})+25=\frac{64}{625}-\frac{28}{25} -\frac{2}{5} +25 \approx 23.58$

Second expression.

$f(x)=9x^{4}-7x^{2} +x+10=9(-\frac{2}{5} )^{4} -7(-\frac{2}{5} )^{2} +\frac{2}{5} +10 \approx 9.5$

Third expression.

$f(x)=10x^{4}-7x^{2} +x+9=10(-\frac{2}{5} )^{4} -7(-\frac{2}{5})^{2} +(-\frac{2}{5})+9 \approx 7.7$

Fourth expression.

$f(x)=25x^{4}-7x^{2} +x+4=25(-\frac{2}{5} )^{4} -7(-\frac{2}{5})^{2} +(-\frac{2}{5})+4 \approx 3.12$

Therefore, neither expression satisfies the given rational root.