Question

Without graphing estimate the x-intercepts of the graph of f(x)=7x^2+9x+1 to the nearest tenth.

Answer 1

The x-intercepts are at -0.1 and -1.2.

We will use the quadratic formula to find these:

`x=(-b\pm √(b^2-4ac))/(2a) \\ \\=(-9\pm √(9^2-4(7)(1)))/(2(7))=(-9\pm √(81-28))/(14) \\ \\=(-9\pm √(53))/(14)=(-9+√(53))/(14)\text{ or } (-9-√(53))/(14) \\ \\=-0.1\text{ or }-1.2`