import tensorflow as tf
import numpy as np
coefficients = np.array([[1],[-20],[25]])

w = tf.Variable([0],dtype=tf.float32)
x = tf.placeholder(tf.float32,[3,1])
cost = x[0][0]*w**2 + x[1][0]*w + x[2][0]
train = tf.train.GradientDescentOptimizer(0.01).minimize(cost)

init = tf.global_variables_initializer()
session = tf.Session()
session.run(init)
print(session.run(w))

for i in range(1000):
    session.run(train,feed_dict={x:coefficients})
    print(session.run(w))
