Which of the quadratic functions has the narrowest graph? y = –2x2 y=-1/2x^2 y = –4x2 y=1/7x^2

Look at the coefficient of x², ignore the positive or negative sign. The larger the coefficient, the narrower the graph. 
in this case, the coefficients are -2, -1/2, -4, and 1/7
ignore the positive or negative sign, 4 is the largest number, so y=-4x² is the narrowest.

Note: the positive/negative sign tells you whether the graph opens upward or downward. It doesn't determine the width of the graph.