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How do you solve a quadratic equation using the quadratic formula?
Write the equation as ax² + bx + c = 0, read off a, b and c, then substitute them into x = (−b ± √(b² − 4ac)) / 2a. Work out the discriminant b² − 4ac first: if it is…
How do you solve simultaneous equations by elimination?
Make the coefficient of one letter the same in both equations, then add or subtract the equations to remove that letter. Solve for the letter that is left, then…
How do you simplify surds?
To simplify a surd, write the number under the root as a product that includes the largest possible square number, then take the square root of that square outside. For…
How do you use SOHCAHTOA to find a side or angle?
In a right-angled triangle, sin θ = opposite ÷ hypotenuse, cos θ = adjacent ÷ hypotenuse and tan θ = opposite ÷ adjacent. Label the sides relative to the angle, pick the…
How do you calculate resistance using Ohm's law?
Ohm's law links voltage, current and resistance: V = IR, where V is the potential difference in volts (V), I is the current in amps (A) and R is the resistance in ohms…
How do you balance a chemical equation?
A balanced equation has the same number of each type of atom on both sides. Count the atoms of each element, then change the large numbers in front of formulas…
What is the difference between ionic and covalent bonding?
Ionic bonding happens between a metal and a non-metal: the metal transfers electrons to the non-metal, forming oppositely charged ions that attract each other. Covalent…
What factors affect the rate of a chemical reaction?
The rate of reaction increases with higher temperature, higher concentration (or pressure for gases), larger surface area and the presence of a catalyst. Collision…
What is the difference between exothermic and endothermic reactions?
An exothermic reaction gives out energy to the surroundings, usually as heat, so the temperature rises. An endothermic reaction takes in energy from the surroundings, so…
How does electrolysis work?
Electrolysis uses electricity to break down an ionic compound that is molten or dissolved, called the electrolyte. Positive ions move to the negative electrode (cathode)…
Explain how a vaccination can prevent an illness.
A vaccine contains a dead, inactive or weakened form of a pathogen, or parts of it, carrying its antigens. White blood cells (lymphocytes) respond by making specific…
How do I write a good introduction for an essay?
A good introduction does three things in a few sentences: it opens with a relevant point about the topic, it shows you understand what the question is asking, and it…
How do you analyse a poem in an exam?
Work out what the poem is about and how the speaker feels, then explain how the poet creates that meaning through language, structure and form. For each point, quote a…
How do you answer a summary question in an English exam?
Read the question to see exactly what information is asked for, find the relevant points in the passage, then rewrite each point in your own words as one short, complete…
How do you form the passé composé in French?
The passé composé is made of two parts: the present tense of avoir or être, followed by the past participle of the main verb. Most verbs use avoir: j'ai mangé (I ate)…
How do you convert a binary number to denary?
Write the place values above each binary digit, starting with 1 on the right and doubling each time to the left (1, 2, 4, 8, 16, 32, 64, 128). Add up the place values…
What is the difference between RAM and ROM?
RAM (random access memory) is volatile: it holds the programs and data currently in use and loses everything when the power is turned off. ROM (read-only memory) is…
What is an algorithm and how do you write one?
An algorithm is a precise, step-by-step set of instructions for solving a problem. It can be written in plain English, as pseudocode or as a flowchart, and then turned…
What were the main causes of the First World War?
Historians often group the long-term causes as militarism, alliances, imperialism and nationalism. The short-term trigger was the assassination of Archduke Franz…