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Worked Solution — Problem of the Week #2 ✅
Here's the full worked solution to this week's problem! Problem: Find the exact area enclosed between f(x) = x² - 4 and the x-axis. Step 1 — Find the x-intercepts: x² - 4 = 0 → (x - 2)(x + 2) = 0 → x = -2 or x = 2 Step 2 — Check whether the curve is above or below the x-axis on [-2, 2]: f(0) = -4 < 0 — the curve is below the x-axis on [-2, 2] Step 3 — Set up the integral and take the absolute value: Area = |∫ from -2 to 2 of (x² - 4) dx| Step 4 — Evaluate: = |[x³/3 - 4x] from -2 to 2| = |(8/3 - 8) - (-8/3 + 8)| = |8/3 - 8 + 8/3 - 8| = |16/3 - 16| = |-32/3| = 32/3 units² The exact area is 32/3 square units. ✅ Common mistake to avoid: always check whether the curve is above or below the x-axis before integrating. If you forgot the absolute value here you would get -32/3 — which is the signed area, not the geometric area. New Problem of the Week drops Monday! 💪
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Quick tip — the chain rule in 3 words 🔗
Students always ask me how to remember the chain rule. Here it is in 3 words: Outside. Leave inside. Multiply. That's it. For any composite function f(g(x)): Step 1 — Differentiate the outside function Step 2 — Leave the inside function exactly as it is Step 3 — Multiply by the derivative of the inside function Example: differentiate sin(x² + 3) Outside function: sin(...) → derivative is cos(...) Leave inside: cos(x² + 3) Multiply by derivative of inside: × 2x Answer: 2x · cos(x² + 3) This works for every chain rule question — exponentials, logs, trig, inverse trig, everything. Try it on this one and post your answer below 👇 Differentiate: f(x) = exp(3x² − 1) Hint: what is the outside function? What is the inside? What is the derivative of the inside?
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Why most students lose marks in IA1 (and how to fix it) 📝
After reviewing hundreds of IA1 responses, the single most common reason students lose marks is this: They list assumptions without justifying them. Here's the difference: ❌ Weak assumption: "I assume the path is straight." ✅ Strong assumption: "I assume the path is straight, as this simplifies the geometric model without significantly affecting the result. In reality, minor curves in the path would have negligible impact on the final answer given the scale of the problem." See the difference? The second one: - States the assumption clearly - Explains WHY you're making it - Acknowledges what effect it would have if it were wrong QCAA markers are looking for mathematical reasoning, not just a list of dot points. Every assumption in your IA1 should follow this structure: What → Why → Impact if wrong Go back to your IA1 draft right now and check every assumption. How many have proper justifications? Drop your subject and year below — I'll let you know what else to focus on for your IA1. 👇
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Success at school
Success at school isn’t built in one big moment. It’s built through the small choices students make every day. ⭐ Showing up. Practising when it’s difficult. Learning from mistakes. Managing your time. Setting clear goals. Staying consistent even when motivation disappears. These habits matter far beyond the next maths test — they build confidence, discipline, independence and resilience. You don’t need to be perfect. You need to keep moving forward. Small steps become progress. Progress becomes confidence. Confidence changes what you believe you’re capable of. 💚 At A Star Maths, we don’t just want students to get the answer right — we want them to develop the habits and mindset that help them succeed long after they leave the classroom. ⭐ Every day counts. Every step matters. #AStarMaths #MathsTutoring #MathsTutor #BrisbaneTutor #BrisbaneMathsTutor #AustralianStudents #HighSchoolMaths #MathsEducation #StudentSuccess #StudyTips
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Success at school
The trick that makes Normal Distribution questions easy 📊
Before you touch your calculator on any Normal Distribution question, do this one thing first: Sketch the curve and shade the region. Here's why it matters: Most students who get Normal Distribution questions wrong don't make algebra errors — they use the wrong tail. They calculate P(X<a) when the question asked for P(X>a), or they forget to subtract from 1. A quick sketch takes 10 seconds and prevents this every single time. Here's the process I teach every student: Step 1 — Draw a bell curve Step 2 — Mark the mean in the centre Step 3 — Mark the value(s) given in the question Step 4 — Shade the region you actually need Step 5 — THEN pick up the calculator This applies to every normal distribution question in the EA — Paper 2 is full of them. Save this post for exam season. 🔖
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