Back to Topic 2.1 โ€” Equations of a line
2.1.1Math AI SL SL16 flashcards

Gradient and y-intercept

Practice Flashcards

Flip to reveal answers
Card 1 of 162.1.1
2.1.1
Question

What does the gradient of a straight line measure?

Click to reveal answer

Track your progress โ€” Sign up free to save your progress and get smart review reminders based on spaced repetition.

All 16 Flashcards โ€” Gradient and y-intercept

Sign up free to track progress and get spaced-repetition review schedules.

Card 1definition

Question

What does the gradient of a straight line measure?

Answer

The gradient measures the steepness and direction of a line โ€” how much y changes for every 1 unit increase in x. Positive gradient โ†’ rises left to right. Negative gradient โ†’ falls left to right. Zero gradient โ†’ horizontal line.

Card 2concept

Question

A line goes up 8 units for every 2 units moved to the right. What is the gradient?

Answer

Gradient = rise รท run = 8 รท 2 = 4. The line goes up by 4 for every 1 unit to the right. This is a positive, fairly steep gradient.

Card 3concept

Question

What does a gradient of โˆ’5 tell you about the line?

Answer

The line falls steeply โ€” for every 1 unit moved right, y drops by 5. Steepness = |โˆ’5| = 5 (compare using absolute value). The negative sign means it slopes downward from left to right.

Card 4concept

Question

Exam trap: Lines have gradients โˆ’4 and 3. A student says gradient 3 is steeper because 3 > โˆ’4. Correct this.

Answer

Wrong โ€” steepness uses absolute value: |โˆ’4| = 4 > |3| = 3. The line with gradient โˆ’4 is steeper. Never compare signed gradient values to decide steepness โ€” always compare |mโ‚| and |mโ‚‚|.

Card 5formula

Question

State the formula for gradient between two points (xโ‚, yโ‚) and (xโ‚‚, yโ‚‚).

Answer

m = (yโ‚‚ โˆ’ yโ‚) / (xโ‚‚ โˆ’ xโ‚) The y-change (rise) goes on top. The x-change (run) goes on the bottom. Use the same pair order for both: subtract in the same direction.

Card 6formula

Question

Find the gradient of the line through (3, 1) and (7, 9).

Answer

m = (9 โˆ’ 1) / (7 โˆ’ 3) = 8 / 4 = 2. y increased and x increased โ†’ positive gradient makes sense. โœ“

Card 7formula

Question

Find the gradient of the line through (โˆ’2, 5) and (4, โˆ’1).

Answer

m = (โˆ’1 โˆ’ 5) / (4 โˆ’ (โˆ’2)) = โˆ’6 / 6 = โˆ’1. Key step: 4 โˆ’ (โˆ’2) = 4 + 2 = 6. Subtracting a negative flips the sign.

Card 8concept

Question

Exam trap: A student writes m = (xโ‚‚ โˆ’ xโ‚)/(yโ‚‚ โˆ’ yโ‚). What is the error and how do you avoid it?

Answer

They have swapped ฮ”y and ฮ”x. The gradient formula is m = ฮ”y/ฮ”x, not ฮ”x/ฮ”y. Fix: always write the formula first โ€” m = (yโ‚‚ โˆ’ yโ‚)/(xโ‚‚ โˆ’ xโ‚) โ€” before substituting numbers.

Card 9definition

Question

What is the y-intercept of a straight line?

Answer

The y-intercept is the point where the line crosses the y-axis โ€” the value of y when x = 0. In y = mx + c, the y-intercept is c, the constant term. Example: y = 4x โˆ’ 7 has y-intercept = โˆ’7, so it crosses at (0, โˆ’7).

Card 10formula

Question

In y = mx + c, which letter is the gradient and which is the y-intercept?

Answer

m is the gradient โ€” it is the coefficient of x. c is the y-intercept โ€” it is the constant term. Example: y = โˆ’2x + 9 โ†’ gradient = โˆ’2, y-intercept = 9.

Card 11formula

Question

State the gradient and y-intercept of y = โˆ’3x + 7. Then write down the coordinates of the y-intercept.

Answer

Gradient m = โˆ’3. y-intercept c = 7. Coordinates of y-intercept: (0, 7).

Card 12concept

Question

Exam trap: A student reads y = 5 โˆ’ 3x and writes gradient = 5, y-intercept = โˆ’3. What went wrong?

Answer

The equation is not in y = mx + c order. Rewrite: y = โˆ’3x + 5. Gradient m = โˆ’3, y-intercept c = 5. Always rearrange into y = mx + c form before reading off m and c.

Card 13concept

Question

What is the gradient of a horizontal line? What about a vertical line?

Answer

Horizontal line: gradient = 0 (no rise โ€” ฮ”y = 0). Vertical line: gradient is undefined โ€” ฮ”x = 0, so we would divide by zero.

Card 14concept

Question

How do you decide which of two lines is steeper?

Answer

Compare the absolute values of their gradients. The line with the larger |m| is steeper. Example: |โˆ’5| = 5 > |2| = 2, so y = โˆ’5x is steeper than y = 2x.

Card 15concept

Question

Line A: y = โˆ’3x + 1. Line B: y = 4x โˆ’ 5. Which crosses the y-axis higher? Which is steeper?

Answer

y-intercepts: A โ†’ c = 1, B โ†’ c = โˆ’5. Line A crosses higher. Steepness: |โˆ’3| = 3 vs |4| = 4. Line B is steeper. Two different comparisons โ€” do them separately.

Card 16concept

Question

Exam trap: A student has y = โˆ’(1/3)x + 9. They write gradient = 1/3. What is wrong?

Answer

They dropped the negative sign. The gradient is m = โˆ’1/3 (negative, because it is โˆ’ times 1/3). The y-intercept is 9. Read the coefficient of x including its sign.

Track your progress with spaced repetition

Sign up free โ€” Aimnova tells you exactly which cards to review and when, so you remember everything before your IB exam.

Start Free
IB Math AI SL Gradient and y-intercept Flashcards | 2.1.1 | Aimnova | Aimnova