Use a Graphing Calculator to Approximate the Real Zeros $$f ( x ) = x ^ { 4 } - 9 x ^ { 2 } + 20$$

Multiple Choice

Use a graphing calculator to approximate the real zeros. Give each zero as a decimal to the nearest tenth.
- $$f ( x ) = x ^ { 4 } - 9 x ^ { 2 } + 20$$

A) $- 1,2.7,2.7 , - 2.7$
B) $2.2 , - 2.2,2 , - 2$
C) $2.2,2$
D) $5 , - 5,4 , - 4$