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Via inspection, one can factorise this via the difference of squares; since a^2-b^2 = (a+b)(a-b), therefore:100-x^2 = (10-x)(10+x)

The first step whenever you are given an equation is to group like terms. By this I mean put all the terms with the same letter next to it together and, in this case, the numbers without a letter. For the...

First we can plug in the values we already know into the equation
we would get:
V² = 12² + (2 x -3 x 18)
then we would seperate the two multiplications on the right ...

So since there are two unknowns in this question, its slightly more difficult than a normal equation where we only have 1 x or y that we're trying to work out. There are two ways to deal with this type of...

W:B = 2:5 Total of 21 litres of paint. We want a ratio of W:B = 1:4 = 2:8
Therefore we must add 3 parts of blue paint
2 + 5 = 7 parts total7 parts = 21L1 part = 3L3 parts = 9L
Ther...