Answer:
B(1, -1)
Step-by-step explanation:
If M(-1, 4) is midpoint of AB then:
[tex]x_M-x_A=x_B - x_M\qquad\quad\ \wedge\qquad y_M-y_A=y_B - y_M\\\\ -1-(-3)=x_B-(-1)\qquad\wedge\qquad -4-(-7)=y_B -(-4)\\\\ -1+3=x_B+1\qquad\qquad\wedge\qquad\ \ -4+7=y_B+4 \\\\ {}\qquad x_B=1\qquad\qquad\wedge\qquad\qquad \ y_B=-1[/tex]
