1. The problem asks: What is the equation if the highest degree is one? 2. In algebra, the degree of an equation is the highest power of the variable in the equation. 3. If the highest degree is one, the equation is called a linear equation. 4. The general form of a linear equation in one variable $x$ is: $$ax + b = 0$$ where $a$ and $b$ are constants and $a \neq 0$. 5. This means the variable $x$ is raised to the power of one, and there are no higher powers like $x^2$, $x^3$, etc. 6. Linear equations represent straight lines when graphed. 7. To solve such an equation, isolate $x$: $$ax + b = 0 \implies ax = -b \implies x = -\frac{b}{a}$$ 8. This gives the solution for $x$ in terms of constants $a$ and $b$. In summary, an equation with highest degree one is a linear equation of the form $ax + b = 0$.