The polynomial p(x) is defined by p(x) = 6x³ + ax²+3x-10, where a is a constant. It is given that (2x – 1) is a factor of p(x).
- (a)Find the value of a and hence factorise p(x) completely.[5]
- (b)Solve the equation p(cosec θ) = 0 for -90° < θ < 90°.[2]
Mark scheme
Marking points from the official mark scheme (Feb/Mar 2024). The mark or mark type is shown in brackets.
- [M1] (a) Substitute x=1/2, equate to zero and attempt solution
- [A1] (a) Obtain a=31
- [M1] (a) Divide by 2x-1 at least as far as 3x² + mx [Or equivalent (for example by inspection, ...).]
- [A1] (a) Obtain 3x² +17x+10
- [A1] (a) Obtain (2x-1)(3x+2)(x+5)
- [M1] (b) Attempt solution of sinθ=k where k is valid constant from answer to part (a)
- [A1] (b) Obtain -11.5 [Or greater accuracy.]
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