span class="identifier">x</span><span> * </span><span class="identifier">a3</span><span>.</span><span class="identifier">x</span><span> + </span><span class="identifier">a3</span><span>.</span><span class="identifier">y</span><span> * </span><span class="identifier">a1</span><span>.</span><span class="identifier">x</span><span>, -</span><span class="identifier">a2</span><span>.</span><span class="identifier">y</span><span> * </span><span class="identifier">a3</span><span>.</span><span class="identifier">x</