Answer:
a = 2, b = -9, c = 3
Step-by-step explanation:
Replacing x, y values of the points in the equation y = a*x^2 + b*x +c give the following:
(-1,14)
14 = a*(-1)^2 + b*(-1) + c
(2,-7)
-7 = a*2^2 + b*2 + c
(5, 8)
8 = a*5^2 + b*5 + c
Rearranging:
a - b + c = 14
4*a + 2*b + c = -7
25*a + 5*b + c = 8
This is a linear system of equations with 3 equations and 3 unknows. In matrix notation the system is A*x = b whith:
A =
1 -1 1
4 2 1
25 5 1
x =
a
b
c
b =
14
-7
8
Solving A*x = b gives x = Inv(A)*b, where Inv(A) is the inverse matrix of A. From calculation software (I used Excel) you get:
inv(A) =
0.055555556 -0.111111111 0.055555556
-0.388888889 0.444444444 -0.055555556
0.555555556 0.555555556 -0.111111111
inv(A)*b
2
-9
3
So, a = 2, b = -9, c = 3
30,77,55,71,19,40,10,5,7,6
She has 27 quarters and 73 dimes.
Write a system of equations.
Let x be the number of quarters, and y be the number of dimes.
x+y=100
0.25x+0.10y=14.05
Solve by substitution:y=100−x
∴0.25x + 0.10(100 - x) = 14.05
0.25x+10−0.10x=14.05
0.15x+10=14.05
0.15x=4.05
x=27
Solve for y now:
y+27=100
y=100−27
y=73
Hence, She has 27 quarters and 73 dimes.
A mathematical equation is a formula that uses the equals sign to represent the equality of two expressions. The meanings of the word equation and its cognates in various languages can vary slightly. For instance, in French, an equation is defined as having one or more variables, whereas, in English, an equation is any well-formed formula that consists of two expressions linked by the equals sign.
Finding the values of the variables that cause the equality to hold true is the first step in solving an equation with variables. The unknown variables are also known as the variables for which the equation must be solved, and the unknown variable values that fulfill the equality are known as the equation's solutions. Equations come in two varieties: identities and conditional equations.
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