without graphing deteermine the number of x intercepts of the graph of y=4x^2-9x+4

for waht values of b does the quadratic function y=x^2+bx+7 have no x intercepts?

for what values does the quadratic function y=x^2-6x+k have two x intercepts?

for what value of k does the quardatic function y=-3x^2-bx+12 have exatcly one x intercept?