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When should I use the imperfect tense and the preterite tense?

We use the imperfect to decribe actions in the past which used to happen regularly, for example: Iba al cine. This can be translated as, "I used to go to the cinema". It is also used to describe th...
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Answered by Susannah H. • Spanish tutor
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When should I use the dative case and the accusative case with the preposition "in"?

The accusative case is used when there is movement from one point to another. For example, in the sentence, "Ich gehe in die Stadt" which means "I'm going into town" we use the accusative...
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Answered by Susannah H. • German tutor
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SOLVE THE FOLLOWING SIMULTANEOUS EQUATIONS: 5x^2 + 3x - 3y = 4, -4x - 6y + 5x^2 = -7

Question: 5x 2 + 3x - 3y = 4, -4x - 6y + 5x 2 = -7.........Step 1: make the y-coefficient equal in both equarions: (y and not x because it has the lowest power so it is easier, but x would also work)...........
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Answered by Alonso M. • Maths tutor
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Use integration by parts to integrate ∫ xlnx dx

∫ u(dv/dx) dx = uv − ∫ v(du /dx)dx is the Integration by Parts formula. If you set u=lnx, differentiation (rememeber from tables) leads to du/dx= 1/x, and dv/dx=x and so v=x^2/2 (raise power by one then divi...
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Answered by Minty M. • Maths tutor
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A gun of mass 10kg fires a bullet of mass 240g at a speed of 300ms-1. What is the speed of the gun's recoil?

First, convert the mass of the bullet into SI units -> 240g=0.24kg The law of the conservation of momentum states that m 1 v 1 =m 2 v 2 . To find the speed of the gun, rearrange for v 1 to give v 1 =m 2 v...
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Answered by Jonny F. • Physics tutor
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