Easy -1.2 This is a straightforward modulus equation requiring only the standard technique of splitting into two cases (0.4x - 0.8 = 2 and 0.4x - 0.8 = -2), then solving two simple linear equations. The decimal coefficients add minimal complexity, and no problem-solving insight is needed beyond applying the basic definition of absolute value.
State non-modulus equation \((0.4x - 0.8)^2 = 4\) or equivalent pair of linear equations
B1
SR: One solution only – B1
Solve 3-term quadratic equation or pair of linear equations
M1
Must see evidence of attempt to solve quadratic for M1 for at least one value of \(x\). For pair of linear equations, there must be a sign difference
Obtain \(-3\) and \(7\)
A1
If extra solutions are given then A0
## Question 1:
| Answer/Working | Mark | Guidance |
|---|---|---|
| State non-modulus equation $(0.4x - 0.8)^2 = 4$ or equivalent pair of linear equations | B1 | SR: One solution only – B1 |
| Solve 3-term quadratic equation or pair of linear equations | M1 | Must see evidence of attempt to solve quadratic for M1 for at least one value of $x$. For pair of linear equations, there must be a sign difference |
| Obtain $-3$ and $7$ | A1 | If extra solutions are given then A0 |
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