Help me plz I do not understand

Mathematics

1 answer:

9966 [12]3 years ago

5 0

It is quite simple actually since it is simple division with the negative rules.
Just simplify the problem and use the negatives to determine if it is positive or negative. (two negatives equal a positive and one negative equals a negative)

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2 trains leave station 238 miles apart at same time toward each other. one at 80mph and other at 90mph. how long will it take fo

lesya692 [45]

$\bf \begin{array}{ccccllll}
&distance&rate(mph)&time(hrs)\\\\
&-----&-----&-------\\\\
\textit{first train}&d&80&t\\
\textit{second train}&238-d&90&t
\end{array}\\\\
-----------------------------\\\\
thus
\\\\

\begin{cases}
\boxed{d}=(80)(t)\\\\
238-\boxed{d}=(90)(t)
\end{cases}$

see the substitution? so.. do the substitution on the 2nd equation, and solve for "t"

bear in mind that, when the trains meet, over the same road, they have been traveling the same distance, one is faster than the other, so the distances differ, but the time does not, is the same for both,

if the first train has been running 45mins and met the second train,
then the second train has also been running for 45mins,
thus "t" is the same for both

5 0

3 years ago

The difference between roots of the quadratic equation x^2+x+c=0 is 6. find c.

DiKsa [7]

Answer:

$\displaystyle c = -\frac{35}{4} = -8.75$ .

Step-by-step explanation:

Let the smaller root to this equation be $m$ . The larger one will equal $m + 6$ .

By the factor theorem, this equation is equivalent to

$a(x - m)(x - (m+6))= 0$ , where $a \ne 0$ .

Expand this expression:

$a\cdot x^{2} - a(2m + 6)\cdot x + a(m^{2} + 6m) =0$ .

This equation and the one in the question shall differ only by the multiple of a non-zero constant. It will be helpful if that constant is equal to $1$ . That way, all constants in the two equations will be equal; $(m^{2} + 6m)$ will be equal to $c$ .

Compare this equation and the one in the question:

The coefficient of $x^{2}$ in the question is $1$ (which is omitted.) The coefficient of $x^{2}$ in this equation is $a$ . If all corresponding coefficients in the two equations are equal to each other, these two coefficients shall also be equal to each other. Therefore $a = 1$ .