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Solve these simultaneous equations: 2x + 3y = 19 and x + 4y = 17.

By multiplying everything in equation 2 by 2, you get 2x + 8y = 34. If you then subtract equation 1 from this you get 5y = 15. Thus y = 3, going back to equation two, and subbing y back in, x + 12 = 17, ther...
JH
Answered by James H. • Maths tutor
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Explain how HIV infects the body once it has entered the host

HIV is a retrovirus that infects specifically T helper cells / CD4 cells in the body.the glycoprotein (envelope protein) on the surface of the virus is able to bind to receptors on CD4 cells, and causes the ...
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Find the equation of the straight line that is tangent to the curve 2x^2 - 5x - 3 =0 when x = 3.

First differentiate 2x 2 - 5x - 3 to get 4x -5. At x = 3, the gradient of the tangent must be 7, and we know it goes through (3, 0) Plug the values into y = mx + c to get the equation of the line, which is y...
SL
Answered by Sarah L. • Maths tutor
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give two features of DNA that is important for DNA replication

complementary base pairing - new strand can be synthesised based on the base sequence on the template strand, so that the resulting strand synthesised is identical to the coding strand. hydrogen bonds betwee...
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Work out 7/(2x^2) + 4/3x as a single fraction in its simplest form.

7/2x 2 + 4/3x = 21/6x 2 + 8x/6x 2 = ( 8x + 21 ) / ( 6x 2 )
CK
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