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Why do melting points decrease down the group 1 and increade down the group 7? (core syllabus: Periodicity)

Elements in the group one (i.e. alkali metals from lithium to francium) exhibit metallic bonding: the positive nuclei are held together thanks to the attraction to delocalised electrons. As the number ...

Answered by Paulina M. • Chemistry tutor

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Show that the following system of equations has an infinite number of solutions. x+y+2z = -2; 3x-y+14z=6; x+2y=-5

Substitute values of one equation into another.

(1) x+y+2z = -2; (2) 3x-y+14z=6; x+2y=-5 (3).

Substitute x in (1) and (2) from (3).

We get -y+2z=3 in (1).

Answered by Egidijus S. • Maths tutor

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When the polynomial 3x^3 +ax+ b is divided by x−2 , the remainder is 2, and when divided by x +1 , it is 5. Find the value of a and the value of b.

Insert the negative values of the divisors and put them into the polynomial. x-2 -> P(2) = 34+2a+b=2 x+1 -> P(-1)=3(-1)+(-1)a+b=5. 22+2a+b=0 -8-a+b=0, then solve the simultaneous equa...

Answered by Egidijus S. • Maths tutor

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Name several sort algorithms of an array, their working principles and their efficency.

Bubble sort (compare two elements and switch them if one of them is higher than other, depending on ordering preference), iterate over the whole array of elements. Efficency O(n²).

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Answered by Egidijus S. • Computing tutor

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