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Unit 3: Parent Functions & Transformations Homework 5: Graphing Quadratic Equations & Inequalities (Standard Form)

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Answer

I can help — please paste the specific problems you need help with. Meanwhile, here’s a concise guide and two worked examples on graphing quadratics in standard form and solving quadratic inequalities.

Quick checklist (standard form)

A quadratic in standard form: $y = ax^2 + bx + c$.

  • Direction: opens up if $a>0$, down if $a<0$.
  • Axis of symmetry: $x_v = -\frac{b}{2a}$.
  • Vertex: $(x_v,\; y_v)$ with $y_v$ found by plugging $x_v$ into the function.
  • y-intercept: $(0,c)$.
  • x-intercepts (real roots) from discriminant $\Delta = b^2 – 4ac$:
  • $\Delta>0$: two real roots, $\Delta=0$: one real root (touches), $\Delta<0$: no real roots.
  • For graphing: find vertex, axis, intercepts, sketch shape and symmetry; plot extra points if needed.

Example 1 — Graph the quadratic

y = $2x^2 – 8x + 6$

The correct answer is: vertex at $(2,-2)$, x-intercepts at $(1,0)$ and $(3,0)$, y-intercept $(0,6)$, parabola opens up.

Explanation and steps:

  1. Axis / vertex: $$x_v = -\frac{b}{2a} = -\frac{-8}{2\cdot2} = 2.$$
  2. Vertex y-value: $$y_v = 2(2)^2 – 8(2) + 6 = 8 – 16 + 6 = -2.$$ Vertex $(2,-2)$.
  3. y-intercept: $c = 6 \Rightarrow (0,6)$.
  4. Roots: use quadratic formula or factor:

$$2x^2 – 8x + 6 = 2(x^2 – 4x + 3) = 2(x-1)(x-3).$$
So x-intercepts: $x=1$ and $x=3$.

  1. Since $a=2>0$, parabola opens up. Sketch using these points and symmetry about $x=2$.

Example 2 — Solve the inequality

Solve $2x^2 – 8x + 6 \le 0$.

The correct answer is: $[1,\,3]$.

Explanation and steps:

  1. Factor like above: $2(x-1)(x-3) \le 0$.
  2. Roots at $x=1$ and $x=3$. Because $a>0$ (opens up), the quadratic is ≤0 between the roots.
  3. Therefore solution interval: $1 \le x \le 3$.

How to solve any quadratic inequality (quick method)

  1. Put everything on one side: $ax^2+bx+c\;(\le, <, \ge, >)\;0$.
  2. Find real roots (if none and $a>0$ then always >0, etc.).
  3. Use a sign chart or remember that a parabola opens up → negative between real roots; opens down → positive between roots. Include endpoints if inequality is non-strict (≤ or ≥).

If you paste your specific homework questions, I’ll solve each one step-by-step and sketch or describe the graph.

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