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X^2+4x-21=0 Solve for x

Quadractics factorise into double brackets like (x-a)(x-b). We ave to find the facors of -21 which add to make +4. 7 and -3 suffice. (x-3)(x+7) Then x will be equal to 3 and -7 for the equation.
JC
Answered by James C. • Maths tutor
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How is mRNA produced in the nucleus of a cell?

Genes in DNA encode protein molecules. The first step of expressing a gene is transferring the information in DNA to a messenger RNA (mRNA) molecule, by a process called transcription. DNA Helicase unwinds t...
JT
Answered by Jamie T. • Biology tutor
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Why does the second derivative tell us something about a function?

Because by looking at the second derivative of a function you are essentially looking at the rate of change of the rate of change. This carries useful information about a function's behaviour and in some sen...
DJ
Answered by Daniel J. • Maths tutor
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Solve this pair of simultaneous equations: 3x + y= 7 and 3x - y = 5

Step 1: Start off by labeling the 2 equations. 3 x + y = 7 will be equation 1. 3 x - y = 5 will be equation 2. Step 2: rearrange equation 1 to make y the subject. 3 x + y = 7 ---> y = 7 - 3 x (here 3 x is...
AG
Answered by Anna G. • Maths tutor
15858 Views

What is a Neurones resting membrane potential and how is it maintained?

On average neurones in the body have a resting membrane potential (RMP) of -70mv. What this means is when inactive/ not excited, the inside of neurone is more negative than the outside of the neurone this is...
IA
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