Question

Given y = 4x + 3, what effect does changing the equation to y = 4x - 3 have on the y-intercept?

A)
graph becomes steeper
B)
no change to y-intercept
C)
graph moves down 3 units
D)
graph moves down 6 units​

Answer 1

graph moves down 6 units​

Explanation:

Y intercept of a line is point on y axis where the line crosses the y-axis.

Since the line is of the slope intercept form y = mx+ c

where m is slope of line and c is y intercept

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Equation of old line : y = 4x + 3

then for equation y = 4x + 3

m: 4 and c = 3

Thus y intercept is +3 unit above the X axis

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Equation of new line : y = 4x - 3

Similarly based on above explanation

m: 4 and c = -3

Thus y intercept is +3 unit below the X axis.

Thus we can see that y intercept has moved downward

Lets calculate no. of units it moved downward

Distance between them is 3 - (-3) = 6 unit

Thus graph moved 6 units downwards.

Steepness of graph depends on slope of line. The slope is 4 for both the lines and hence there is no change in steepness.

Thus correct answer is graph moves down 6 units​