DepEd MELC reviewer for Grade 9 Mathematics, Quarter 2. Study the rules, worked formulas, and exam hacks below.
1
Variation
| Type | Equation |
|---|---|
| Direct | y = kx |
| Inverse | y = k/x |
| Joint | y = kxz |
| Combined | y = kx/z |
๐ก Exam Hack
"Direct" โ as one goes up, the other goes up. "Inverse" โ as one goes up, the other goes down.
2
Rational Exponents and Radicals
a^(m/n) = โฟโ(aแต) โa ร โb = โ(ab)
โ ๏ธ Common Mistake
โ(a+b) is NOT โa + โb. You cannot split a radical over addition.
3
Simplifying Radicals
Simplify by factoring out perfect squares: โ50 = โ(25ยท2) = 5โ2. Rationalize denominators by multiplying by the radical.
4
Worked Example
y varies directly as x; y = 12 when x = 3. Find k and y when x = 5.
k = y/x = 12/3 = 4 โ y = 4(5) = 20
๐ Quick Recap โ Master These
Before your test, make sure you can confidently do each of the following:
- Explain and apply Variation.
- Explain and apply Rational Exponents and Radicals.
- Explain and apply Simplifying Radicals.
- Explain and apply Worked Example.
Re-read any section above where you hesitate, then try the worked example again without looking.