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The point P(-3,9) belongs to a line intercepting the origin. Find the equation of the line.

We are told that the line passes through the origin O (0,0) and the point P (-3,9). First we need to find the gradient of the line m; this is given by m = (change in y)/(change in x), hence m = (9-0)/(-3-...

Answered by Valeria B. • Maths tutor

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Solve algebraically the simultaneous equations: x^2 + y^2 = 25 and y - 3x = 13

Firstly we should look at the question and notice that the two possible methods are substitution or elimination. We should then notice that since one equation is a quadratic and the other linear, then the...

Answered by Aviv S. • Maths tutor

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What are the steps contained in action potential production?

The first step of the production of an action potential is a stimulus, which is a signal that excites the cell membrane causing Na+ ion channels to open. These channels are called voltage gated ion channe...

Answered by Megan M. • Biology tutor

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The enthalpy of combustion of ethanol is −1371 kJ mol−1 . The density of ethanol is 0.789 g cm−3 . Calculate the heat energy released in kJ when 1 dm3 of ethanol is burned.

1 dm3 of ethanol is equal to 1000 cm3, so the mass of ethanol used is =density x volume = 0.789 g cm-3 x 1000 cm3 = 789gMolar mass of ethanol = (2x12)+(6x1) +(1x16)= 46 g mol-1Moles of ethanol = mass/mola...

Answered by Sophie L. • Chemistry tutor

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