不等式をグラフで解く

To solve an inequality graphically, select x-values, calculate corresponding y-values using the function, and plot the graph on a coordinate plane. Shade the region where the inequality holds true. The x-values in the shaded area represent the solution set. This visual approach makes it easy to identify which values satisfy the inequality condition.

The shaded region on a quadratic graph shows where the inequality condition is satisfied. For greater than or equal to inequalities, the shaded part indicates the solution. For less than or equal to inequalities, the unshaded region represents the solution. The x-values within these regions are the values that satisfy the quadratic inequality.

Plot both functions on the same coordinate plane and identify their intersection points. These x-values mark the boundaries of the solution set. Determine where one graph lies above, below, or on the other graph based on the inequality symbol. The x-values in the appropriate region form the complete solution to the inequality.

A quadratic inequality involves a parabola, while a linear inequality involves a straight line. When comparing a quadratic with a linear function, both graphs are plotted together to find intersection points. These points define where the parabola lies above or on the line, determining the solution set. The graphical method works similarly for both, but the curve shapes differ.

Graphical methods are useful in finance to compare monthly expenses with budget constraints. By plotting expense and budget functions, the shaded region shows where expenses remain below the budget line. This visual representation helps identify acceptable spending ranges and makes financial planning more intuitive and easier to understand.

When a curve lies below the x-axis, the y-values are negative. For an inequality like x² − 4x + 2 < 0, the solution consists of x-values where the curve is below the x-axis. These x-values satisfy the inequality condition. The interval where the curve remains below the axis represents the complete solution set.

The graphical method provides an intuitive visual representation of where inequalities are satisfied. By examining graphs of equations in two variables, students can quickly identify solution intervals and understand the nature of functions. This visual approach makes abstract algebraic concepts concrete and helps students see the relationship between the inequality condition and the corresponding region on the graph.