Question

What is the value of k? with a= 4 and b= -7​

Answer 1

Answer:

The value of k ⇨ $-\frac{121}{16}$  

Explanation:

⟺ Substitute a = 4 and b = -7 in the equation.

From $y=ax^2+3x+b$

Our new equation is $y=4x^2+3x-7$

⟺ Use the formula of finding k value.

$k=\frac{4ac-b^2}{4a}$

⟺ Substitute a = 4 b = 3 and c = -7 in the formula. (Arranged Expression)

$k=\frac{4(4)(-7)-(3)^2}{4(4)}\\k=\frac{-112-9}{16}\\k=-\frac{121}{16}$

If you are curious where k-value/term comes form, it comes from this equation.

$y=a(x-h)^2+k$

Answer 2

Answer:

k= -7/4

Step-by-step explanation:

y=ax^2+3x+b, a=4 b=-7

y=4x^2+3x-7

where y=0 at the intersection

4x^2+3x-7=0

by using factorisation method

product=-28

sum=3

factors=7,-4

(4x^2-4x)+(7x-7)=0

4x(x-1)+7(x-1)=0

(4x+7)(x-1)=0

4x+7=0, x-1=0

x=-7/4, x=1

therefore, k= -7/4