diff --git a/Makefile b/Makefile
index 323f755..5b8227c 100644
--- a/Makefile
+++ b/Makefile
@@ -4,9 +4,8 @@ CFLAGS := -Wall -g -std=c90
 LDFLAGS := -lm
 
 LIB_DIR := ./lib/nr/ansi
-LIB_INCLUDE := $(LIB_DIR)/other
-LIB_SRCS := $(LIB_DIR)/recipes/machar.c
-LIB_OBJS := $(patsubst %.c,$(BUILD_DIR)/lib/%.o,$(notdir $(LIB_SRCS)))
+LIB_INCLUDE := -I$(LIB_DIR)/other
+
 
 HW_DIR := ./hws
 
@@ -15,6 +14,15 @@ ifeq ($(strip $(hw)),)
 else
 	TARGET_NAME := hw$(hw)
 	SRC_DIR := $(HW_DIR)/hw$(hw)
+	ifeq ($(strip $(hw)),1)
+		LIB_SRCS := $(LIB_DIR)/recipes/machar.c
+	else ifeq ($(strip $(hw)),2)
+		LIB_SRCS := $(LIB_DIR)/other/nrutil.c $(LIB_DIR)/recipes/rtflsp.c $(LIB_DIR)/recipes/rtbis.c $(LIB_DIR)/recipes/rtsec.c $(LIB_DIR)/recipes/rtnewt.c $(LIB_DIR)/recipes/rtsafe.c $(LIB_DIR)/recipes/zbrak.c $(LIB_DIR)/recipes/bessj0.c $(LIB_DIR)/recipes/bessj1.c
+	else
+		LIB_SRCS := ""
+	endif
+	LIB_OBJS := $(patsubst %.c,$(BUILD_DIR)/lib/%.o,$(notdir $(LIB_SRCS)))
+
 endif
 
 ifeq ($(strip $(TARGET_NAME)),)
@@ -24,8 +32,10 @@ else
     TARGET_EXEC := $(BUILD_DIR)/$(TARGET_NAME).out
     TARGET_SRCS := $(wildcard $(SRC_DIR)/*.c)
     TARGET_OBJS := $(patsubst %.c,$(BUILD_DIR)/hw$(hw)/%.o,$(notdir $(TARGET_SRCS)))
+	TARGET_INCLUDE := -I$(SRC_DIR)
 	OBJS := $(TARGET_OBJS) $(LIB_OBJS)
 	SRCS := $(TARGET_SRCS) $(LIB_SRCS)
+	INCLUDE := $(TARGET_INCLUDE) $(LIB_INCLUDE)
 all: run
 endif
 
@@ -43,13 +53,13 @@ build: init $(TARGET_EXEC)
 
 $(TARGET_EXEC): $(OBJS)
 	@echo "링킹 중: $@"
-	$(CC) $(CFLAGS) $(LDFLAGS) $^ -o $@ 
+	$(CC) $(CFLAGS) $^ -o $@ $(LDFLAGS)
 
 $(OBJS): %.o:
 	@echo "컴파일 중: $@"
 	$(eval TARGET_C_BASENAME := $(patsubst %.o,%.c,$(notdir $@)))
 	$(eval FOUND_SRC := $(foreach src,$(SRCS),$(if $(filter $(TARGET_C_BASENAME),$(notdir $(src))),$(src))))
-	$(CC) $(CFLAGS) $(LDFLAGS) -I $(LIB_INCLUDE) -c $(FOUND_SRC) -o $@
+	$(CC) $(CFLAGS) $(INCLUDE) $(LDFLAGS) -c $(FOUND_SRC) -o $@ 
 
 run: clean build
 	@echo "실행 시작"
@@ -58,4 +68,4 @@ run: clean build
 
 dist:
 	mkdir -p out
-	zip -j -9 out/$(TARGET_NAME).zip $(TARGET_SRCS) 
\ No newline at end of file
+	zip -j -9 out/$(TARGET_NAME).zip $(TARGET_SRCS)
\ No newline at end of file
diff --git a/hws/hw2/main.c b/hws/hw2/main.c
new file mode 100644
index 0000000..26efcd4
--- /dev/null
+++ b/hws/hw2/main.c
@@ -0,0 +1,88 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "nr.h"
+
+void dbessj0(float x, float *y, float *dy) {
+    *y = bessj0(x);
+    *dy = -bessj1(x);
+}
+
+int main() {
+    /*
+    1. using zbrak, find all possible intervals with roots.
+    2. and use routines and enumerate all roots.
+    */
+
+    float a = 1.0, b = 10.0;
+    float xacc = 0.000001;
+
+    int n = 23;
+    float *xb1 = calloc(sizeof(float), n);
+    float *xb2 = calloc(sizeof(float), n);
+    int nb;
+
+    int i;
+    zbrak(bessj0, a, b, n, xb1, xb2, &nb);
+
+    for (i = 1; i <= nb; i++) {
+        printf("[%f, %f]\n", xb1[i], xb2[i]);
+    }
+
+    float *roots_bisect = calloc(sizeof(float), nb);
+    float *roots_linter = calloc(sizeof(float), nb);
+    float *roots_secant = calloc(sizeof(float), nb);
+    float *roots_newt = calloc(sizeof(float), nb);
+    float *roots_newtsafe = calloc(sizeof(float), nb);
+    
+    for (i = 0; i < nb; i++) {
+        float l = xb1[i + 1];
+        float r = xb2[i + 1];
+        roots_bisect[i] = rtbis(bessj0, l, r, xacc);
+        roots_linter[i] = rtflsp(bessj0, l, r, xacc);
+        roots_secant[i] = rtsec(bessj0, l, r, xacc);
+        roots_newt[i] = rtnewt(dbessj0, l, r, xacc);
+        roots_newtsafe[i] = rtsafe(dbessj0, l, r, xacc);
+    }
+
+    printf("besection roots: ");
+    for (i = 0; i < nb; i++) {
+        printf("%f ", roots_bisect[i]);
+    }
+    printf("\n");
+
+    printf("lin-interpoalation roots: ");
+    for (i = 0; i < nb; i++) {
+        printf("%f ", roots_linter[i]);
+    }
+    printf("\n");
+
+    printf("secant roots: ");
+    for (i = 0; i < nb; i++) {
+        printf("%f ", roots_secant[i]);
+    }
+    printf("\n");
+
+    printf("newton-raphson roots: ");
+    for (i = 0; i < nb; i++) {
+        printf("%f ", roots_newt[i]);
+    }
+    printf("\n");
+
+    printf("newton with bracketing roots: ");
+    for (i = 0; i < nb; i++) {
+        printf("%f ", roots_newtsafe[i]);
+    }
+    printf("\n");
+
+    /* free */
+    free(xb1);
+    free(xb2);
+
+    free(roots_bisect);
+    free(roots_linter);
+    free(roots_secant);
+    free(roots_newt);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/hws/hw2/muller.c b/hws/hw2/muller.c
new file mode 100644
index 0000000..e69de29
diff --git a/hws/hw2/muller.h b/hws/hw2/muller.h
new file mode 100644
index 0000000..e69de29