title: ValueError: Shape must be rank 2 but is rank 1 for 'MatMul' (op: 'MatMul') with input shapes: [2], [2,3]
body: <p>I'm so news to Tensorflow . I already search for same questions,but i can't understand. there is the code .Hope you can help me. </p>
  
  <p><strong>Code:</strong></p>
  
  <pre><code>import tensorflow as tf
  
  w1 = tf.Variable(tf.random_normal([2,3],stddev=1,seed=1))
  w2 = tf.Variable(tf.random_normal([3,3],stddev=1,seed=1))
  
  x = tf.constant([0.7,0.9])
  
  a = tf.matmul(x, w1)
  y = tf.matmul(a, w2)
  
  sess = tf.Session()
  
  sess.run(w1.initializer)
  sess.run(w2.initializer)
  
  print(sess.run(y))
  sess.close()
  </code></pre>