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Two Truths and a Lie - Mathematics

For each question, you are given three math-related statements and... STOP IT! An evil demon has manipulated them so now there's a false statement in every question! Can you identify each false statement?
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Last updated: April 2, 2022
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First submittedMarch 24, 2022
Times taken31
Average score60.0%
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1. Which statement is false?
If n is odd, then n2 must be odd
The sum of a geometric series is given by the formula: S = a / (1 − r)
If y = kx for some constant k, then dy/dx = k
The sum to infinity of a convergent geometric series is given by the formula S = a / (1 − r); the sum of the first n terms of a geometric series is given by S = a(1 − rn) / (1 − r) or S = a(rn − 1) / (r − 1)
2. Which statement is false?
The following identity is always true: sin(A + B) = sin A + sin B
The Pythagorean theorem states that: a2 + b2 = c2
The distributive property of multiplication is: a(b + c) = ab + ac
sin(A + B) = sin A cos B + cos A sin B
3. Which statement is false?
If y = sin x, then dy/dx = cos x
If f'(x) = 0 for some value of x, then (x,f(x)) must be the maximum point of the curve
The graph of y = 1 / x has asymptotes at the coordinate axes
It could be the local maximum point or the local minimum point, not necessarily the maximum point
4. Which statement is false?
The slope of a line is given by the formula: m = (y2 − y1) / (x2 − x1)
The graph of y = f(x + 3) is a translation of the graph of y = f(x) 3 units to the left
All angles in a quadrilateral must be smaller than 180°
Not necessarily; one of the angles could be reflex
5. Which statement is false?
(a + b)2 = a2 + b2
The following identity is always true: logab = 1 / logba (a≠1, b≠1)
Any non-zero number raised to the power of zero is 1
(a + b)2 = a2 + 2ab + b2
6. Which statement is false?
The identity sin2x + cos2x = 1 is true for all values of x
The power of a power rule is: (am)n = am + n
The modulus of vector x = 3i + 4j is 5
The power of a power rule should be: (am)n = amn
7. Which statement is false?
Euler's identity states that: e + 1 = 0
The graph of y = 2x + 1 meets the x-axis at the point (−½,0)
The following sequence is arithmetic: 1, 3, 6, 10, ...
The difference between two consecutive terms in an arithmetic sequence must be equal
8. Which statement is false?
The quadratic equation x2 − 2x − 3 = 0 has only one solution
The binomial expansion of (x + 1)3 is: x3 + 3x2 + 3x + 1
The power of a product rule is: (ab)n = anbn
Calculating the discriminant of the equation: b2 − 4ac = (−2)2 − 4(1)(−3) = 4 + 12 = 16 > 0, so there are two solutions
9. Which statement is false?
For all values of x, sin 2x = 2 sin x cos x
The only prime number that is also an even number is 2
For all values of x, tan x = sin x / cos x
tan x is undefined when cos x = 0 (i.e. when x = 90°, 270°, ...)
10. Which statement is false?
When converting degrees to radians, you divide by (360/π)
The formula used to convert Celsius temperatures into Fahrenheit, F = 1.8C + 32, is a linear function
The Greek letter Σ (sigma) is used to signify a sum
You should divide by (180/π)
+2
Level 76
Apr 2, 2022
The first question makes no sense. A series is an infinite sum. So the 'sum of a geometric series' does not mean anything.

Also if you say it's wrong because it's not specified that the series converges, then I would argue that e.g. the a, b and c in the Pythagorean theorem need to be specified before you could say it's correct.