Live practice

\[\begin{aligned}f &= \frac{R}{2}\\&= +15\end{aligned}\] cm, \(u=-20\) cm.

The image lies behind the mirror and is virtual, erect and diminished.

Carbon dioxide, water, chlorophyll and light are required. Chlorophyll traps solar energy to reduce carbon dioxide using water:

Glucose is stored or converted into other organic compounds; oxygen is released as a by-product.

Each soap ion has a hydrophobic hydrocarbon tail and a hydrophilic ionic head. Tails embed in oily dirt while heads remain in water. On agitation many soap ions surround a dirt droplet and form a micelle, with dirt trapped inside and charged heads outside. Repulsion between charged surfaces keeps the droplets suspended. Rinsing removes these micelles with the water.

Copper develops a green coating of basic copper carbonate in moist air. Lemon and tamarind contain acids that react with and dissolve this basic coating, producing soluble copper salts. Removal of the coating exposes the shiny copper surface below.

A: pH 4, B: pH 1, C: pH 11, D: pH 7 and E: pH 9.

• Neutral: D (pH 7)
• Strongly alkaline: C (pH 11)
• Strongly acidic: B (pH 1)
• Weakly acidic: A (pH 4)
• Weakly alkaline: E (pH 9)

Hydrogen-ion concentration decreases as pH increases. Therefore increasing \([\ce{H+}]\) means arranging from highest pH to lowest pH:

Define the sample space and count each favourable outcome once.

The final value lies in [0,1]; complement pairs also sum to one, providing an independent check.

Simplify the expression before substitution and preserve one-sided information.

Substitution into the original expression verifies the stated domain and final value.

Translate every condition into an equation and retain exact values throughout the ellipse calculation.

The last line satisfies the original conditions and supplies every requested part.

Translate every condition into an equation and retain exact values throughout the straight-line calculation.

The last line satisfies the original conditions and supplies every requested part.

Use the sequence definition or geometric-progression formula, keeping the first-term offset explicit.

The displayed substitutions cover every requested part and verify the result against the original data.