Algebra · real student question

Write y = (1/4)(x + 1) - 2 in slope-intercept form and state the slope and y-intercept.

Question

Write

y=14(x+1)2y=\frac{1}{4}(x+1)-2

in slope-intercept form y=mx+cy=mx+c, and state the slope and yy-intercept.

Step-by-step solution

  1. Recognise the starting form. y=14(x+1)2y=\tfrac14(x+1)-2 is a shifted version of point-slope form: the coefficient outside the bracket is already the slope, and the goal is to expose the yy-intercept.

  2. Distribute the 14\tfrac14 over the bracket. Both terms inside must be multiplied:

    y=14x+14(1)2=14x+142y=\frac{1}{4}x+\frac{1}{4}(1)-2=\frac{1}{4}x+\frac{1}{4}-2

  3. Combine the constants over a common denominator. Write 22 as 84\tfrac84:

    142=1484=74\frac{1}{4}-2=\frac{1}{4}-\frac{8}{4}=-\frac{7}{4}

  4. State the slope-intercept form.

    y=14x74y=\frac{1}{4}x-\frac{7}{4}

    so the slope is m=14m=\tfrac14 and the yy-intercept is c=74=1.75c=-\tfrac74=-1.75.

  5. Check with two points. At x=0x=0 the original gives 14(1)2=1.75\tfrac14(1)-2=-1.75, matching the intercept \checkmark. At x=3x=3 the original gives 14(4)2=1\tfrac14(4)-2=-1, and the new form gives 3474=1\tfrac34-\tfrac74=-1 \checkmark. The slope check: yy rose by 0.750.75 while xx rose by 33, and 0.753=14\tfrac{0.75}{3}=\tfrac14 \checkmark.

Answer

y=14x74,m=14,c=74y=\frac{1}{4}x-\frac{7}{4},\qquad m=\frac{1}{4},\quad c=-\frac{7}{4}

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