Answer:
(a) yes
(b) no
(c) yes
(d) yes
Step-by-step explanation:
You want to know which of these equations is linear.
For the purpose here, we will define a linear equation as one that graphs as a straight line. (Other definitions may give different answers.)
In general, a linear equation will have a highest degree of 1. (It may be 0.)
The equation of choice (b) has degree 2, so is not a linear equation.
The attached graph shows the only equation that is not linear is choice (b).
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Additional comment
In some branches of mathematics, an equation of the form y = mx+b is not a linear equation. In basic algebra, that is the model of a linear equation, for any values of m and b.