Jika garis 2x−7y+5=0 direfleksi terhadap sumbu y dan dilanjutkan translasi T= -8 4 , maka bayangan garis tersebut adalah …. 2x−7y+17=0 2x−7y−17=0 7x+2y+17=0 2x+7y−17=0 2x−7y−17=0

Mathematics

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2 steps
  1. Reflect the line 2x−7y+5=02x - 7y + 5 = 0 against the y-axis.

    When a point (x,y)(x,y) is reflected across the y-axis, its new coordinates (x′,y′)(x',y') are given by x′=−xx' = -x and y′=yy' = y.
    From these relations, we can express xx and yy in terms of x′x' and y′y':
    x=−x′x = -x'
    y=y′y = y'
    Substitute these into the original line equation:

    2(−x′)−7(y′)+5=02(-x') - 7(y') + 5 = 0 −2x′−7y′+5=0-2x' - 7y' + 5 = 0

    Multiply by -1 to get a positive coefficient for xx:

    2x′+7y′−5=02x' + 7y' - 5 = 0

    So, the equation of the line after reflection is 2x+7y−5=02x + 7y - 5 = 0.

  2. Translate the reflected line 2x+7y−5=02x + 7y - 5 = 0 by the translation vector T=(−84)T = \begin{pmatrix} -8 \\ 4 \end{pmatrix}.

    When a point (x′,y′)(x',y') is translated by T=(ab)T = \begin{pmatrix} a \\ b \end{pmatrix}, its new coordinates (x′′,y′′)(x'',y'') are given by x′′=x′+ax'' = x' + a and y′′=y′+by'' = y' + b.
    Here, a=−8a = -8 and b=4b = 4.
    So, x′′=x′−8  ⟹  x′=x′′+8x'' = x' - 8 \implies x' = x'' + 8
    And y′′=y′+4  ⟹  y′=y′′−4y'' = y' + 4 \implies y' = y'' - 4
    Substitute these into the equation of the reflected line:

    2(x′′+8)+7(y′′−4)−5=02(x'' + 8) + 7(y'' - 4) - 5 = 0 2x′′+16+7y′′−28−5=02x'' + 16 + 7y'' - 28 - 5 = 0 2x′′+7y′′+(16−28−5)=02x'' + 7y'' + (16 - 28 - 5) = 0 2x′′+7y′′−17=02x'' + 7y'' - 17 = 0

    The final equation of the line after translation is 2x+7y−17=02x + 7y - 17 = 0.

    The correct option is 2x+7y-17=0.

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