A teacher knows that 15% of the pencils borrowed by her students are NOT returned. The teacher
2 answers:
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The general form of a quadratic (second degree) equation is
, where
is called the Discriminant.
The Discriminant determines how many roots the equation will have as follows:
i) if D>0, the equation has 2 roots.
ii) if D=0, the equation has 1 double root.
iii) if D<0, the equation has no roots.
In our equation,
, a=1, b=-5, c=7
so the discriminant is D=(-5)^2-4*1*7=25-28<0
Thus the equation has no roots.
Remark: the equation has no roots in the Real numbers, but it has 2 roots in a larger set of numbers to be discussed in the future, the Complex numbers.
The Discriminant determines how many roots the equation will have as follows:
i) if D>0, the equation has 2 roots.
ii) if D=0, the equation has 1 double root.
iii) if D<0, the equation has no roots.
In our equation,
so the discriminant is D=(-5)^2-4*1*7=25-28<0
Thus the equation has no roots.
Remark: the equation has no roots in the Real numbers, but it has 2 roots in a larger set of numbers to be discussed in the future, the Complex numbers.
Answer:
(x, y) = (40, 30)
Step-by-step explanation:
A graphing calculator can show you the solution to this system of equations is (x, y) = (40, 30). That is the point of intersection where the two lines cross.
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An algebraic solution can be found by using the substitution method. An expression for y can be found using the second equation:
y = 110 -2x . . . . . . subtract 2x from both sides
Using this in the first equation gives ...
3x -4(110 -2x) = 0 . . . . substitute for y
11x = 440 . . . . . . . . . simplify, add 440
x = 40 . . . . . . . . . . divide by 11
y = 110 -2(40) = 30
The solution is (x, y) = (40, 30).
