The following diagram shows the lines x – 2y – 4 = 0, x + y = 5 and the point P(1, 1). A line is drawn from P to intersect with x – 2y – 4 = 0 at Q, and with x + y = 5 at R, so that P is the midpoint of [QR]. Find the exact coordinates of Q and of R.

Step-by-step explanation:

Let (a, b) represent the coordinates of point Q on line x -2y -4 = 0. Then we know that ...

  a -2b -4 = 0

  a -2b = 4

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If P is the midpoint of QR, then ...

  R = 2P -Q = 2(1, 1) -(a, b) = (2 -a, 2 -b)

We know this point satisfies the equation for the other line:

  x + y = 5

  (2 -a) +(2 -b) = 5

  a + b = -1 . . . . . . . . . . . rearrange to standard form

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To find the solution to these two equations, we can subtract the first from the second:

  (a +b) -(a -2b) = (-1) -(4)

  3b = -5

  b = -5/3

  a = -1 -1b = -1 -(-5/3) = 2/3

The point Q is (a, b) = (2/3, -5/3).

The point R is ...

  R = (2 -a, 2 -b) = (2 -2/3, 2 -(-5/3)) = (4/3, 11/3)

The exact coordinates of Q and R are ...

  Q(2/3, -5/3), R(4/3, 11/3)

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Comment on the GeoGebra solution

The points can be found by reflecting either line across point P. Where that reflected line intersects the other line is one of the points of interest. Of course, the other is its reflection in P. You may recognize the equation for line b' (hidden in the diagram) as matching the second equation we derived above.

answer

a,b, and d

explanation

a reflection angle is more than

but less than;

an angle that measures

is a reflex angle.(true)

an angle that measures less than

is acute.(true)

provided we are considering angles greater or equal to zero.

an acute angle lies in the range.

an obtuse angle is less than 180° but more than 90°

an angle that measures 300° is obtuse (false)

an angle that measures 65° is an acute angle.(true)

coins of silver or gold

step-by-step explanation: