Easy -1.8 This is a straightforward algebraic rearrangement requiring only two steps: multiply both sides by 3/2, then take the square root. It involves basic manipulation of a simple quadratic formula with no problem-solving or conceptual challenge—purely mechanical recall of inverse operations.
- or \([b^2 =] \dfrac{ka}{c}\) or \([b^2 =] \dfrac{a}{kc}\) (oe)
M1
Allow M1 for triple-decker or quadruple-decker fraction or decimals eg \(\dfrac{1.5a}{c}\), if no recovery later
- Correctly taking square root of their \(b^2\), including the \(\pm\) sign
M1
Square root must extend below the fraction line
## Question 6:
$[b =] \pm\sqrt{\dfrac{3a}{2c}}$ (oe www) | 3 marks |
- $[b^2 =] \dfrac{3a}{2c}$ soi | M2 | eg M2 for $[b =]\sqrt{\dfrac{3a}{2c}}$
- or $[b^2 =] \dfrac{ka}{c}$ or $[b^2 =] \dfrac{a}{kc}$ (oe) | M1 | Allow M1 for triple-decker or quadruple-decker fraction or decimals eg $\dfrac{1.5a}{c}$, if no recovery later
- Correctly taking square root of their $b^2$, including the $\pm$ sign | M1 | Square root must extend below the fraction line
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