O-LevelAdditional MathematicsQuadratic functions4037/22 · May/June 2019 · Q55 Marks
Express 5x² - 15x+1 in the form p(x+q)² +r, where p, q and r are constants.
- (i)Express 5x² - 15x+1 in the form p(x+q)² +r, where p, q and r are constants.[3]
- (ii)Hence state the least value of x²-3x+0.2 and the value of x at which this occurs.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.
- [B3] (i) 5(x-1.5)² -10.25 isw (B1 for each of p, q, r correct in correctly formatted expression; allow correct equivalent values. If B0 then SC2 for 5(x−1.5)–10.25 or SC1 for correct values but other incorrect format)
- [B2] (ii) STRICT FT their part (i); their -10.25 / 5 is least value when x = their 1.5. (B1 STRICT FT for each)
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