Question

The x-coordinate of the vertex of the function y=-x²+bx+3 is 10. Determine the y-coordinate of the vertex.

Answer 1

• 103

Explanation:

Given function:

• y = -x² + bx + 3

The x-coordinate of a quadratic function y = ax² + bx + c is determined by:

• x = -b/2a

The given function has:

• x = 10, and a = -1

Find the value of b:

• 10 = -b / -2
• b = 20

The function is:

• y = -x² + 20x + 3

The y-coordinate of the vertex is:

• y = -(10²) + 20*10 + 3 = -100 + 200 + 3 = 103

Answer 2

Solution given:

y = -x² + bx + 3

we have

The x-coordinate of a quadratic function y = ax² + bx + c is determined by:

x =
`( - b)/(2a)`

we have

x = 10, and a = -1

Substituting value of a in -b/2a

we get

b = 20

now

The y-coordinate of the vertex is:

y = -(10²) +20*10+ 3 = -100 + 200 + 3 = 103 is your answer.