Maths Olympiad Prep

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Algebra Difficulty 2.3 Junior Find the answer

The line with equation y=3x+5y = 3x + 5 is translated 2 units to the right. What is the equation of the resulting line?

A number or a short expression. Spacing and $ signs are ignored.

Solution

The line with equation y=3x+5y = 3x + 5 has slope 3 and yy-intercept 5. Since the line has yy-intercept 5, it passes through (0,5)(0, 5). When the line is translated 2 units to the right, its slope does not change and the new line passes through (2,5)(2, 5). A line with slope mm that passes through the point (x1,y1)(x_1, y_1) has equation yy1=m(xx1)y - y_1 = m(x - x_1). Therefore, the line with slope 3 that passes through (2,5)(2, 5) has equation y5=3(x2)y - 5 = 3(x - 2) or y5=3x6y - 5 = 3x - 6, which gives y=3x1y = 3x - 1. Alternatively, we could note that when the graph of y=3x+5y = 3x + 5 is translated 2 units to the right, the equation of the new graph is y=3(x2)+5y = 3(x - 2) + 5 or y=3x1y = 3x - 1.

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