document.write( "Question 3193: How would you write an equation for a line that has an x-intercept of -1 and a y-intercept of 4? \n" ); document.write( "

Algebra.Com's Answer #1380 by drglass(89) $\"\"$ $\"About$

You can put this solution on YOUR website!
First, remember the equation of a line,

\n" ); document.write( "y = mx + b
\r
\n" ); document.write( "\n" ); document.write( "where m is the slope of the line and b is the y-intercept.\r
\n" ); document.write( "\n" ); document.write( "The question tells you two points on the line. The first point is the x-intercept, we will call it P1 = (-1, 0), the second point is the y-intercept, which we will call P2 = (0, 4). We can find the slope of the line by

\n" ); document.write( "m = $\"%28y2-y1%29%2F%28x2-x1%29\"$ = $\"%284+-+0%29%2F%280+-+%28-1%29%29\"$ = 4

\n" ); document.write( "Since we already know the value of the y-intercept is 4, the equation of the line is:

\n" ); document.write( "y = $\"4x+%2B+4\"$

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\n" ); document.write( "You can check this by setting x = 0,

\n" ); document.write( " $\"y+=+4%2A0+%2B+4+=+4\"$
\r
\n" ); document.write( "\n" ); document.write( "So we get the point (0,4) from this equation.

\n" ); document.write( "Next set y = 0,

\n" ); document.write( " $\"0+=+4x+%2B+4\"$ subtract 4 from both sides to isolate x

\n" ); document.write( " $\"-4+=+4x\"$ divide by 4 on both sides to get x by itself

\n" ); document.write( " $\"-1+=+x\"$

\n" ); document.write( "This is the x-intercept (-1, 0) for the line. Our equation gives us the two points used to define the problem, therefore, it must be the correct equation. \n" ); document.write( "

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