Answer:
[tex]y=-\dfrac{1}{4}x^2-x+\dfrac{21}{4}[/tex]
Step-by-step explanation:
Intercept form of a quadratic equation
[tex]y=a(x-p)(x-q)[/tex]
where:
Given:
Substitute the given values into the formula and solve for a:
[tex]\begin{aligned} y&=a(x-p)(x-q)\\\\\implies-6&=a(5-(-7))(5-3)\\-6&=a(12)(2)\\-6&=24a\\a&=\dfrac{-6}{24}\\\implies a&=-\dfrac{1}{4}\end{aligned}[/tex]
Substitute the given x-intercepts and the found value of a into the formula:
[tex]\implies y=-\dfrac{1}{4}(x+7)(x-3)[/tex]
Expand to standard form:
[tex]\implies y=-\dfrac{1}{4}(x^2-3x+7x-21)[/tex]
[tex]\implies y=-\dfrac{1}{4}(x^2+4x-21)[/tex]
[tex]\implies y=-\dfrac{1}{4}x^2-x+\dfrac{21}{4}[/tex]