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800 most-asked Class 11 & 12 (+1 / +2) questions across Physics, Chemistry, Maths and Biology — each with a model answer and the exact marking-scheme points examiners reward. Revise smart, walk in calm.
MathsClass 113 marksmedium
Complex Numbers and Quadratic Equations
Express (3 + 4i)/(1 - 2i) in the form a + i b.
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Multiply numerator and denominator by the conjugate of the denominator (1 + 2i): [(3 + 4i)(1 + 2i)]/[(1 - 2i)(1 + 2i)]. Numerator = 3 + 6i + 4i + 8i^2 = 3 + 10i - 8 = -5 + 10i. Denominator = 1^2 + 2^2 = 5. So the result = (-5 + 10i)/5 = -1 + 2i.
multiply by conjugate of denominator
Marking-scheme points
- ✓Multiply by conjugate (1 + 2i)
- ✓Numerator = -5 + 10i; denominator = 5
- ✓Result = -1 + 2i
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Complex Numbers and Quadratic Equations
Solve the equation x^2 - 2x + 5 = 0.
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Here a = 1, b = -2, c = 5. Discriminant = b^2 - 4ac = 4 - 20 = -16. So x = [2 +/- sqrt(-16)]/2 = [2 +/- 4i]/2 = 1 +/- 2i. The roots are 1 + 2i and 1 - 2i.
x = [-b +/- sqrt(b^2 - 4ac)]/(2a)
Marking-scheme points
- ✓Discriminant = 4 - 20 = -16
- ✓sqrt(-16) = 4i
- ✓x = (2 +/- 4i)/2 = 1 +/- 2i
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Complex Numbers and Quadratic Equations
Find the square root of the complex number -5 + 12i.
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Let sqrt(-5 + 12i) = a + i b. Squaring: a^2 - b^2 + 2ab i = -5 + 12i. So a^2 - b^2 = -5 and 2ab = 12 (ab = 6). Also |z| = sqrt((-5)^2 + 12^2) = sqrt(25 + 144) = 13, so a^2 + b^2 = 13. Adding a^2 - b^2 = -5 and a^2 + b^2 = 13 gives 2a^2 = 8, a^2 = 4, a = +/-2; then b^2 = 9, b = +/-3. Since ab = 6 is positive, a and b have the same sign. Hence sqrt(-5 + 12i) = +/- (2 + 3i).
(a + ib)^2 = a^2 - b^2 + 2ab i
Marking-scheme points
- ✓Let sqrt = a + ib; a^2 - b^2 = -5, 2ab = 12
- ✓a^2 + b^2 = |z| = 13
- ✓Solve: a = +/-2, b = +/-3 -> +/- (2 + 3i)
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Linear Inequalities
Solve 5x - 3 >= 3x - 5 and show the solution set on a number line.
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Linear Inequalities
Solve the system of inequalities 2x - 1 < 5 and 3x + 2 > -4, and find the common solution.
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Linear Inequalities
The longest side of a triangle is three times the shortest side and the third side is 2 cm shorter than the longest side. If the perimeter of the triangle is at least 61 cm, find the minimum length of the shortest side.
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Permutations and Combinations
How many distinct arrangements can be made using all the letters of the word 'MATHEMATICS'?
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Permutations and Combinations
Find the value of n if nC2 = 15.
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Permutations and Combinations
How many 4-digit numbers can be formed using the digits 0 to 9 if no digit is repeated?
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Permutations and Combinations
From 7 men and 5 women, in how many ways can a committee of 5 members be formed consisting of exactly 3 men and 2 women?
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Binomial Theorem
Expand (2x - 3)^4 using the binomial theorem.
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Binomial Theorem
Find the coefficient of x^5 in the expansion of (x + 3)^8.
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Binomial Theorem
Find the term independent of x in the expansion of (x^2 - 1/x)^6.
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Binomial Theorem
Using the binomial theorem, evaluate (sqrt2 + 1)^4 + (sqrt2 - 1)^4.
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Binomial Theorem
Find the coefficient of x^6 y^3 in the expansion of (x + 2y)^9.
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Sequences and Series
Find the sum of the first 20 terms of the arithmetic progression 3, 7, 11, 15, ...
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Sequences and Series
The sum of three numbers in AP is 24 and their product is 440. Find the numbers.
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Sequences and Series
Find the sum of the first 6 terms of the geometric progression 5, 15, 45, ...
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Sequences and Series
Find the sum to infinity of the geometric progression 1 + 1/3 + 1/9 + 1/27 + ...
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Sequences and Series
Find the sum of the squares of the first 10 natural numbers, that is 1^2 + 2^2 + ... + 10^2.
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