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Marissa M.
Six years of tutoring experience
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Pre-Calculus
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Question:

Preform the requested operation or operations: f(x) = x^2+4 g(x) = sqrt(x-9) Find f(g(x)).

Marissa M.

f(g(x)) = (sqrt(x-9))^2+4 f(g(x)) = x-9+4 f(g(x)) = x-5

Chemistry
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Question:

Calculate the molality when 75.0 grams of MgCl_2 is dissolved in 500.0 g of solvent.

Marissa M.

75.0g ---------------- = 0.788 mol 95.2 g/mol 0.788 mol -------------- = 1.58 m 0.500 kg Molality, or molal concentration, measures the concentration of solute in solution compared to the mass of the solvent. It is represented by moles of solute divided my kilograms of solvent. And is denoted with the symbol m representing the unit mol/kg. An important note about molality is that it is in no way dependent on the identity of the solute, merely the amount of it in solution.

Biology
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Question:

Explain the difference between passive and active transport and facilitated diffusion?

Marissa M.

Passive transport is a method by which materials are moved across a semi-permeable membrane from an area of high concentration to an area of low concentration. Facilitated diffusion is a type of passive transport that uses a transport protein in order to move larger or charged molecules across a membrane. These transport or carrier proteins however are very specific and only pair with a molecule or molecules of the appropriate shape and charge to fit their channel. Neither passive transport nor facilitated diffusion require ATP, an energy source, in order to move materials across a membrane. Active transport on the other hand requires both a transport protein and an input of ATP. This is because active transport is the only method by which materials can enter/exit a membrane against the membrane's concentration gradient.

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