How do you find all zeros of #f(x)=x^4-x^3-20x^2#?
1 Answer
Dec 12, 2017
Explanation:
#"take out a common factor of "x^2#
#f(x)=x^2(x^2-x-20)#
#"the factors of - 20 which sum to - 1 are - 5 and + 4"#
#rArrf(x)=x^2(x-5)(x+4)#
#"to find zeros set "f(x)=0#
#rArrx^2(x-5)(x+4)=0#
#"equate each factor to zero and solve for x"#
#x^2=0rArrx=0" with multiplicity 2"#
#x-5=0rArrx=5#
#x+4=0rArrx=-4#
