positive: two sign changes, max two real roots.
negative: zero sign changes, zero real roots
min number of non-real roots:
4-(2-0)=2
f(x)=2x^4+5x^2-6x+9
Use Descartes' Rule of Signs to determine the possible numbers of positive and negative real zeros.
2 answers
one flip in f(x) from 5 x^2 to - 6 x
second from -6 x to +9
no flips in f(-x) = 2x^4 + 5x^2 + 6x + 9
so two or zero positive real roots
check with
http://www.emathhelp.net/calculators/algebra-1/descartes-rule-of-signs-calculator/
second from -6 x to +9
no flips in f(-x) = 2x^4 + 5x^2 + 6x + 9
so two or zero positive real roots
check with
http://www.emathhelp.net/calculators/algebra-1/descartes-rule-of-signs-calculator/
1 answer