Solving by Completing: Error Analysis & Misconceptions

Mathematics
Grade 8
10 questions
~20 mins
1 views0 downloads

About This Worksheet

A worksheet focusing on solving quadratics by completing the square, highlighting common errors and misconceptions for Grade 8 students.

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Solving by Completing: Error Analysis & Misconceptions

Subject: MathematicsGrade: Grade 8
Name:
Date:
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Untitled Worksheet

Grade Grade 8
A

Fluency & Practice

Answer all questions. Show your working in the grid spaces provided.
1.
Complete the square to solve: x^2 + 6x = 7.
[2 marks]
2.
Rewrite the quadratic x^2 + 4x + 1 = 0 by completing the square.
[3 marks]
3.
Solve for x: x^2 + 8x + 16 = 0 using completing the square.
[2 marks]
B

Problem Solving & Reasoning

Work through the multi-step problems carefully, explaining each step.
1.
A ball is thrown upward and its height h(t) in meters is modeled by h(t) = -4t^2 + 16t + 3. Complete the square to find the time when the ball reaches its maximum height.
[4 marks]
2.
Given the quadratic equation x^2 + 10x + 6 = 0, students made an error by completing the square incorrectly. Identify and explain the mistake.
[3 marks]
C

Real-world Applications

Apply completing the square to these real-life scenarios.
1.
A rectangular garden has a length that is 4 meters more than its width. Its area is modeled by A(w) = w^2 + 4w. Complete the square to find the width when the area is 36 square meters.
[3 marks]
D

Challenge & Extension

Attempt these advanced problems to extend your understanding.
1.
Solve the quadratic: 2x^2 - 8x + 5 = 0 by completing the square, showing all steps.
[4 marks]
2.
Explain why completing the square might be more advantageous than the quadratic formula in certain situations.
[2 marks]
E

Mixed Review & Error Analysis

Identify and correct the common mistakes in the following problems.
1.
A student attempted to solve x^2 + 6x = 9 by completing the square but made an error. The student's steps are: (x + 3)^2 = 0. What mistake did they make?
[2 marks]
2.
Identify the mistake: students tried to complete the square for x^2 + 2x + 1 = 0 and wrote (x + 1)^2 = 0 without solving for x.
[2 marks]

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Details

Created
1/1/2026
Updated
1/1/2026
Type
worksheet