diff --git a/glslUtil/glslUtil.c b/glslUtil/glslUtil.c
index 6c3757a..9341264 100644
--- a/glslUtil/glslUtil.c
+++ b/glslUtil/glslUtil.c
@@ -108,12 +108,15 @@ void guMatrixFrustum(guMatrix4x4 *m,
             mult[i][j] = 0.0;
         }
     }
-    mult[0][0] = 2 * near / (right - left);
-    mult[0][2] = (right + left) / (right - left);
-    mult[1][1] = 2 * near / (top - bottom);
-    mult[1][2] = (top + bottom) / (top - bottom);
-    mult[2][2] = - (far + near) / (far - near);
-    mult[2][3] = - 2 * far * near / (far - near);
+    GLfloat rl = right - left;
+    GLfloat tb = top - bottom;
+    GLfloat fn = far - near;
+    mult[0][0] = 2 * near / rl;
+    mult[0][2] = (right + left) / rl;
+    mult[1][1] = 2 * near / tb;
+    mult[1][2] = (top + bottom) / tb;
+    mult[2][2] = - (far + near) / fn;
+    mult[2][3] = - 2 * far * near / fn;
     mult[3][2] = -1.0;
     guMatrixMult(m, m, &mult);
 }
@@ -131,10 +134,11 @@ void guPerspective(guMatrix4x4 *m, GLfloat fovy, GLfloat aspect,
         }
     }
     GLfloat f = 1.0 / tan(fovy / 2.0);
+    GLfloat nf = near - far;
     mult[0][0] = f / aspect;
     mult[1][1] = f;
-    mult[2][2] = (far + near) / (near - far);
-    mult[2][3] = (2 * far * near) / (near - far);
+    mult[2][2] = (far + near) / nf;
+    mult[2][3] = (2 * far * near) / nf;
     mult[3][2] = -1.0;
     guMatrixMult(m, m, &mult);
 }