Question

If one zero of the quadratic polynomial (k – 1)x² – kx + 1 is -4, then the value of k is

(a) \(\frac{-5}4\) 

(b) \(\frac{5}4\) 

(c) \(\frac{-4}3\) 

(d) \(\frac{4}3\)

Answer 1

Since –4 is a zero of (k – 1) x² + kx + 1, 

we have: 

(k – 1) × (-4)² + k × (-4) + 1 = 0 

⇒ 16k – 16 – 4k + 1 = 0 

⇒ 12k – 15 = 0

⇒ k = \(\frac{15}{12}\)

⇒ k = \(\frac{5}{4}\)