For each parabola, you have to do a system of equation with the line y = x - 5 and find which of them has one real solution.
For that you can solve the systems and find the roots, but you can also use the rule that to have one real solution the discriminant of the quadratiic equation (b^2 - 4ac) has to be zero.
1)
y = x - 5
y = x^2 + x - 4
=> x - 5 = x^2 + x - 4
=> x^2 + 1 = 0
It is easy to tell, by simple inspection, that this equation has not real solutions.
2)
y = x -5
y = x^2 + 2x - 1
=> x - 5 = x^2 + 2x - 1
=> x^2 + x + 4 = 0
discriminant = b^2 - 4ac = 1^2 - 4(1)(4) = 1 - 16 = - 15
A negative discriminant means that there are not real solutions.
3)
y = x - 5
y = x^2 + 6x + 9
x - 5 = x^2 + 6x + 9
=> x^2 + 5x + 14 = 0
=> b^2 - 4ac = 5^2 - 4(1)(14) = 25 - 56 = - 31 => no real solutions
4)
y = x - 5
y = x^2 + 7x + 4
x - 5 = x^2 + 7x + 4
=> x^2 + 6x + 9 = 0
=> b^2 - 4ac = 6^2 - 4(1)(9) = 36 - 36 = 0 => the system has one real solution.
By the way, that solution is easy to find because you can factor the equation as: (x + 3)^2 = 0 => x = - 3
Answer:
c. (3, 2)
Step-by-step explanation:
Equating the values of y :
- -x + 5 = x - 1
- x + x = 5 + 1
- 2x = 6
- <u>x = 3</u> [x-coordinate of the solution]
Finding y by substituting x in one of the equations :
- y = x - 1
- y = 3 - 1
- <u>y = 2</u> [y-coordinate of the solution]
Solving :
- Solution = (x, y)
- Solution = (3, 2)
Three million, one hundred and fifty two thousand, three hundred and eight.
Answer:
4050 sq. feet.
Step-by-step explanation:
Fencing is done on three sides of the rectangular area.
Given that there are 180 feet of fence available.
Then 2L + W = 180 ........(1), where L = length and W = width, of the rectangular plot.
Now, the area of the plot is given by A = LW
Now, from equation (1), we ger A = L (180 - 2L) ..... (2)
Then differentiating with respect to L in the both sides we get,
{Since condition for Area to be maximum is
}
⇒ L = 45 feet.
Now, from equation (2), we have
square feet.
The answer would be 8.6 miles. use the pythagorean theorem to solve.