# math

Given the quadratic function f(x) = x2 – 18x + 81, find a value of x such that f(x) = 16.

1. Solve the equation

x^2-18x+81=16
x^2-18x+65=0

posted by Mgraph
2. f(x) = x^2 – 18x + 81
f(x) = 16
substituting the value of f(x) to the quadratic equation,
16 = x^2 - 18x + 81
0 = x^2 - 18x + 81 - 16
0 = x^2 - 18x + 65
0 = (x-13)(x-5)
thus,
x = 13 and x = 5

hope this helps~ :)

posted by Jai

## Similar Questions

1. ### Math

i'm a bit stuck with this.. 145/18 = x + x^2 what does x equal to? multiply each term by 18, then re-arrange to get 18x^2 + 18x - 145 = 0 This quadratic does not factor, so use the quadratic formula to get your two answers.
2. ### math

Still looking at how to solve these... Both are cubic polynomials? 43x^3 + 13x^2 + 18x - 456 = 0 DO I divide first by x-1? 2x(3x+2)^2=312 Honestly: I would graph the equations and find the roots first. I don't see them off hand.

Please explain to me how to do the following problems, I don't understand them. Thanks! Find the x-intercepts (if any) for the graph of the quadratic function. 1.f(x) = (x + 2)2 - 4 Find the y-intercept for the graph of the
4. ### Algebra Problems

Please check my answers. Find the coordinates of the vertex for the parabola defined by the given quadratic function. 1.f(x) = (x - 4)2 - 4 -I got (4,-4) Find the axis of symmetry of the parabola defined by the given quadratic
5. ### Algebra

Please check my answers. Find the coordinates of the vertex for the parabola defined by the given quadratic function. 1.f(x) = (x - 4)2 - 4 -I got (4,-4) Find the axis of symmetry of the parabola defined by the given quadratic
6. ### Algebra

Please check my answers. Find the coordinates of the vertex for the parabola defined by the given quadratic function. 1.f(x) = (x - 4)2 - 4 -I got (4,-4) Find the axis of symmetry of the parabola defined by the given quadratic
7. ### Math: quadratic function and equation

Given the quadratic function y=x^2-x+k-1 and line y=x+1, find the number of points that their graphs have in common. (Assume k>4)
8. ### Algebra

Can you please help me with the following problems? Find the coordinates of the vertex for the parabola defined by the given quadratic function. 1.f(x) = (x - 4)2 - 4 Find the axis of symmetry of the parabola defined by the given
9. ### math

A quadratic function has its vertex at the point (-9,3). The function passes through the point (2,-1). Find the quadratic and linear coefficients and the constant term of the function.
10. ### College Algebra

The graph of a quadratic function f(x) is shown above. It has a vertex at (-2,4) and passes the point (0,2). Find the quadratic function y=a(x-(-2))^2+4 y=a(x+2)+4 2=a(x+2)+4 -4 -4 -2=a(0+2)/2 -1+ a function -1(x+2)+4 ? Im not

More Similar Questions