You should know that:
(a+b)(a+b)(a+b)
=a(a+b)(a+b)+b(a+b)(a+b)
=a(a²+2ab+b²)+b(a²+2ab+b²)
=a³+2a²b+ab²+a²b+2ab²+b³
=a³+3a²b+3ab²+b³
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If a=5x and b=-4y
(5x+(-4y))³
=(5x-4y)³
=(5x)³+3(5x)²(-4y)+3(5x)(-4y)²+(-4y)³
=125x³+3(25x²)(-4y)+15x(16y²)-64y³
=125x³+75x²(-4y)+240xy²-64y³
=125x³-300x²y+240xy²-64y³
The general form is ax²+bx+c=0,
so at least we know b has to be 0. None of the values match unless we multiply everything by 4. That leads to answer B, a=1, b=0 and c=20
[1], [3] => a = 49,000/2 = 24,500 => b +c = 24,500 => c = 24,500 - b;
[2] => 25*24,500 + 20b + 15c = 1,052,000 => 20b + 15c = 1,027,500;
20b + 15*(24,500 - b) = 1,027,500 => 5b = 733,500 => b = 146,700 =>
c = - 122,200;
