f.4,,mathz,,can the value of k be 1? and,,,

a) Sub k=1 into y
i.e., y= (1-1)x^2+3x-4
y= 3x-4
general formula y=mx+c is a st.line
a st.line can never have 2 x-intercepts
therefore k cannot be 1.

b) by delta = b^2 -4ac
i.e., 3^2-4(k-1)(-4) = 9+16k-16 = 16k - 7
according to the data given, there're 2 different x-intercepts
therefore delta > 0
i.e., 16k-7 > 0
16k > 7
k > 7/16

A part 用代數計到INTERCEPT得1個 (JUST A 補充TO第1個答題的人)
B part　｛－ｂ〔＋／－〕ｂ^2-4ａｃ｝　／２ａ　＞０　因此can求得不等式(inequality)來求ｋ（於已知ａｂｃ情況下）