What is the slope of the line 2x + 3y = 6?
- (a)−2⁄3
- (b)3⁄2
- (c)−3⁄2
- (d)2⁄3
Answer
Why
Correct — A.
Rewrite 2x + 3y = 6 in the form y = mx + c:
Subtract 2x: 3y = −2x + 6
Divide by 3: y = −(2⁄3)x + 2
The coefficient of x is the slope: m = −2⁄3 → option (a)
Why the others are wrong
- (b)3⁄2 — 3⁄2 is the negative reciprocal of −2⁄3: the slope of a line perpendicular to 2x + 3y = 6, not of the line itself.
- (c)−3⁄2 — −3⁄2 has the right sign but turns the fraction over: it is −b⁄a. The slope of ax + by = c is −a⁄b = −2⁄3.
- (d)2⁄3 — 2⁄3 drops the minus sign. Moving 2x across gives 3y = −2x + 6, so the slope is negative.
Concept
For a line ax + by + c = 0, the slope is m = −a⁄b. It comes from solving for y and reading the coefficient of x.
Here a = 2 and b = 3, so m = −2⁄3. A negative slope means y falls as x rises.
Check with the intercepts: the line meets the axes at (3, 0) and (0, 2), and (0 − 2) ÷ (3 − 0) = −2⁄3. It falls from 2 on the y-axis to 0 at x = 3, the drop a negative slope describes.
Key facts
- The slope of ax + by + c = 0 is −a⁄b.
- In y = mx + c, m is the slope and c is the y-intercept.
- Two perpendicular lines, neither vertical, have slopes whose product is −1.
Study next
Common traps
- Writing the slope as −b⁄a, or as a⁄b without the minus sign: the rule is −a⁄b.
- Giving the perpendicular slope 3⁄2 when the question asks for the line's own slope.
15 Sep 2025, 16:00, Quant Q.23 asks for the slope perpendicular to y = −3x + 7, keyed 1⁄3 (option c).
17 Sep 2025, 16:00, Quant Q.16 finds a slope from two points, (2, 3) and (4, 7), keyed 2 (option a).
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