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Consider the Matrix M (below). Find the determiannt of the matrix M by using; (a) cofactor expansion along the first row, (b) cofactor expansion along the second column

Matrix M is -2 1 -4 1 -1 5 3 0 2 Let A be a square nxn matrix. Then, for each entry Aij (where 1 </= i < n, 1 </= j < n), the minor of Aij is A(^i;^j), the determinant of the (n - 1) (n - 1) matr...
ET
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Why do ionic compounds like NaCl conduct electricity when dissolved but not when they’re solid, whereas metals conduct electricity when they’re solid?

Firstly, it's important to recognise that ionic compounds and metals are two different structures. Ionic compounds consist of positively charged ions and negatively charged ions held together by strong elect...
HB
Answered by Hannah B. • Chemistry tutor
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When using cm3 as the unit for volume to calculate the concentration why must you divide the cm3 by 1000?

As I’m sure you already know, the units of concentration are mol dm -3 . So before we calculate concentrations we must convert the volume with units cm 3 to dm 3 . 1 dm is the equivalent of 10 cm . So, by cu...
HB
Answered by Hannah B. • Chemistry tutor
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Solve the quadratic equation: x^2 - 2x - 15 = 0

We need to find numbers that multiply together to give -15. This could be -1 and 15, 1 and -15, -3 and 5, 3 and -5. The numbers we need must add up to -2 as well (from -2x term). Therefore our set must be 3 ...
SK
Answered by Sabrina K. • Maths tutor
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Factorise completely ( x − 4x^3)

(x-4x 3 ) = x(1-4x 2 ) Just taking a factor of x out of both terms Within the inner bracket we have a difference of two squares. 1 2 =1 and (2x) 2 =4x 2 therefore we can write x(1-4x 2 ) = x(1-2x)(1+2x)
EC
Answered by Edward C. • Maths tutor
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