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Practice: systems of equations

Practice: systems of equations

1

{2x+y=7x−y=2\displaystyle {\begin{cases}2x+y=7\\ x-y=2\end{cases}}
Which of the pairs is the solution of the system: (3,1)\displaystyle (3,1), (2,3)\displaystyle (2,3), (4,−1)\displaystyle (4,-1)?
Explain by substituting.

2

Here are the lines of the system {y=x−1y=−x+5\displaystyle {\begin{cases}y=x-1\\ y=-x+5\end{cases}}
Mark the point where they meet on the graph.
Write the solution of the system, and check it by substituting into both equations.

y=x−1\displaystyle y=x-1
y=−x+5\displaystyle y=-x+5

3

Without solving: how many solutions does each system have – one, none or infinitely many?
Explain.

a

{y=4x−1y=4x+3\displaystyle {\begin{cases}y=4x-1\\ y=4x+3\end{cases}}

b

{y=−2x+1y=x+1\displaystyle {\begin{cases}y=-2x+1\\ y=x+1\end{cases}}

c

{x+y=32x+2y=6\displaystyle {\begin{cases}x+y=3\\ 2x+2y=6\end{cases}}

4

Solve by substitution.

a
    b
      c
        5

        Solve by comparison.

        a
          b
            6

            Solve by adding or subtracting the equations.
            In parts 3 and 4 first multiply an equation by a number – or both of them.

            a
              b
                c
                  d
                    7

                    The sum of two numbers is 50, and their difference is 14.
                    Find the two numbers.
                    Write a system of equations and solve it.

                      8

                      2 notebooks and 3 pens cost 27 ₪.
                      4 notebooks and 1 pen cost 29 ₪.
                      How much is a notebook, and how much a pen?
                      Write a system of equations and solve it.

                        A notebook (₪)

                          / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                          / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                          A pen (₪)

                            / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                            / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                            9

                            Grandma’s yard has hens and rabbits.
                            Together they have 20 heads and 56 legs.
                            How many hens and how many rabbits are in the yard?
                            Write a system of equations and solve it.

                              Hens

                                / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                                / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                                Rabbits

                                  / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                                  / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                                  10

                                  In a basketball game a team scored 23 baskets: 2-point baskets and 3-point baskets.
                                  The team scored 52 points in the game.
                                  How many baskets of each kind did the team score?
                                  Write a system of equations and solve it.

                                    2-point baskets

                                      / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                                      / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                                      3-point baskets

                                        / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                                        / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                                        11

                                        There are two gyms in town:
                                        Gym A charges a 100 ₪ sign-up fee plus 30 ₪ a month.
                                        Gym B charges 50 ₪ a month, with no sign-up fee.
                                        On the graph, x\displaystyle x is the number of months and y\displaystyle y the total price in shekels; gym B is the dashed line.
                                        Mark the point where the lines meet on the graph.
                                        Write an equation and solve it: after how many months do the two gyms cost the same?
                                        Yoav wants to train for a whole year. Which gym should he join?

                                        y=30x+100\displaystyle y=30x+100
                                        y=50x\displaystyle y=50x