Answer: B
If \(25x^2 - 20ax + b\) is a perfect square, then the roots of the equation \(25x^2 - 20ax + b = 0\) will be equal. That means the discriminant will be zero. \(\therefore (-20a)^2 - 4 \times 25 \times b = 0\) or, \(400a^2 - 100b = 0\) or, \(100b = 400a^2\) or, \(b = 4a^2\)
If \(25x^2 - 20ax + b\) is a perfect square, then the roots of the equation \(25x^2 - 20ax + b = 0\) will be equal. That means the discriminant will be zero. \(\therefore (-20a)^2 - 4 \times 25 \times b = 0\) or, \(400a^2 - 100b = 0\) or, \(100b = 400a^2\) or, \(b = 4a^2\)