Question
Find b and c so that y=-1x^2+bx+c has vertex (-5,-4). Please help ASAP I'm having a really hard time on this question!!!
Answers
clement
parabola equation y=ax²+bx+c
the x- coordinate is -b/2a
so for
y=-x²+bx+c
ax²+bx+c=-x²+bx+c
a=-1
b/2(1)=-5
b=-10
hence you have the equation to be
y=-x²-10x+c
x²+10x-c=-y
(2)²+10(2)-c=4
4+20-c=4
24-c=4
-c=4-24
c=20
the x- coordinate is -b/2a
so for
y=-x²+bx+c
ax²+bx+c=-x²+bx+c
a=-1
b/2(1)=-5
b=-10
hence you have the equation to be
y=-x²-10x+c
x²+10x-c=-y
(2)²+10(2)-c=4
4+20-c=4
24-c=4
-c=4-24
c=20
clement
do you think you can help me check my question
clement
i think i made a typo b=10
not -10
because of the negative value of a
that shouldn't be a problem right
the ideal is the same,so you do the correction
not -10
because of the negative value of a
that shouldn't be a problem right
the ideal is the same,so you do the correction
oobleck
You want y=-1x^2+bx+c with vertex at (-5,-4)
The vertex at (-5,-4) means that
y = a(x+5)^2 - 4
So now you have
ax^2 + 10ax + 21 = -x^2+bx+c
(a,b,c) = (-1,10,21)
The vertex at (-5,-4) means that
y = a(x+5)^2 - 4
So now you have
ax^2 + 10ax + 21 = -x^2+bx+c
(a,b,c) = (-1,10,21)