O-LevelAdditional MathematicsIndices and surds4037/22 · Oct/Nov 2017 · Q25 Marks
Solve the equation 2x^1.5 + 6x^-0.5 / x^0.5+ 5x^-0.5 = x.
- Solve the equation 2x^1.5 + 6x^-0.5 / x^0.5+ 5x^-0.5 = x.[5]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.
- [M1] 2x^1.5 + 6x^-0.5 = x(x^0.5 + 5x^-0.5); Attempt to multiply by x^0.5 + 5x^-0.5 or x^0.5 or divide by x^0.5
- [A1] 2x^1.5 + 6x^-0.5 = x^1.5 + 5x^0.5 or x^1.5 - 5x^0.5 + 6x^-0.5 = 0; Simplified numerical powers
- [M1] x²-5x+6=0; M1dep obtain a three term quadratic. Allow errors in signs and coefficients but not powers
- [M1] (x-3)(x-2) = 0; Solve a three term quadratic
- [A1] x = 3 or 2 only
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