We are given the following function and asked to find its
x-intercepts.
f(x)=x−12−3x+4
Let's start with recalling that an
x- is a point where the graph intersects the
x-axis. The
y-coordinate of this point is
0. Hence, to find the
x-intercepts of the given function we can substitute
f(x) with
0 and solve it for
x.
0=x−12−3x+4
First, we will rewrite the right-hand side as one . In order to do this, we will expand the first fraction by
3 and the second one by
x−1 so that they have a .
0=3(x−1)2(3)−3(x−1)(x+4)(x−1)
Now we are able to subtract the fractions.
0=3(x−1)2(3)−3(x−1)(x+4)(x−1)
0=3(x−1)2(3)−(x+4)(x−1)
0=3(x−1)6−(x+4)(x−1)
0=3(x−1)6−(x2−x+4x−4)
0=3(x−1)6−x2+x−4x+4
0=3(x−1)-x2−3x+10
The fraction can be equal to
0 only if its numerator is equal to
0. This means that we need to solve the following equation.
-x2−3x+10=0
Let's first change the signs by multiplying both sides of the equation by
-1. Then we will solve it by .
-x2−3x+10=0
x2+3x−10=0
x2+5x−2x−10=0
x(x+5)−2(x+5)=0
(x−2)(x+5)=0
According to the , at least one of the parentheses should be equal to
0.
x−2=0x+5=0 ⇒ x=2x=-5
We got that the zeroes, or
x-intercepts of the function are
-5 and
2. The answer is
D.