diff --git a/SICP/exercise_1_7.janet b/SICP/exercise_1_7.janet
new file mode 100644
index 0000000..efd0e64
--- /dev/null
+++ b/SICP/exercise_1_7.janet
@@ -0,0 +1,27 @@
+(defn square [x] (* x x))
+
+(defn good-enough? [previous current]
+  (>=
+    (* current 0.001)
+    (math/abs (- current previous))))
+
+(defn average [x y]
+  (/ (+ x y) 2))
+
+(defn improve [guess x]
+  (average guess (/ x guess)))
+
+(defn sqrt-iter [prev guess x]
+  (if (good-enough? prev guess)
+          guess
+          (sqrt-iter guess (improve guess x) x)))
+
+(defn sqrt [x]
+  (sqrt-iter 0.0 x x))
+
+(var i 0.0000001)
+(while (<= i 1000000000000.0)
+  (def meas (sqrt i))
+  (def rel (/ (- meas (math/sqrt i)) meas))
+  (print (string/format "Relative error %f=%f, %f" (math/sqrt i) meas rel))
+  (set i (* i 3.141519)))
diff --git a/SICP/exercise_1_8.janet b/SICP/exercise_1_8.janet
new file mode 100644
index 0000000..34c5986
--- /dev/null
+++ b/SICP/exercise_1_8.janet
@@ -0,0 +1,26 @@
+(defn square [x] (* x x))
+
+(defn good-enough? [previous current]
+  (>=
+    (* current 0.0001)
+    (math/abs (- current previous))))
+
+(defn improve [guess x]
+  (/
+    (+ (* 2 guess) (/ x (square guess)))
+    3))
+
+(defn cbrt-iter [prev guess x]
+  (if (good-enough? prev guess)
+          guess
+          (cbrt-iter guess (improve guess x) x)))
+
+(defn cube-root [x]
+  (cbrt-iter 0.0 x x))
+
+(var i 0.0000001)
+(while (<= i 1000000000000.0)
+  (def meas (cube-root i))
+  (def rel (/ (- meas (math/cbrt i)) meas))
+  (print (string/format "Relative error %f=%f, %f" (math/cbrt i) meas rel))
+  (set i (* i 3.141519)))