Tham KY's answer to :)'s Secondary 4 E Maths Singapore question.
Hello, how did u get from square root( l^2+b^2 ) to the next step?
Using (x+y)²= x²+y²+2xy expansion, rearrange gets x²+y²= (x+y)²-2xy.
Must remember, used very often even in JC...
Must remember, used very often even in JC...
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