Day 4 ยท Topic 4 of 6

Standard Form: Ax + By = C

Convert between slope-intercept and standard form. Write equations from real-world scenarios.
๐Ÿ“ 10 Questionsโฑ ~35 minโœ… answers-topic4.html

๐ŸŽต Len Fact โ€” Standard Form in Music!

In "Kagamine Len no Bousou" (Len's Spree), Len sings at speeds up to 200 syllables per minute! If ticket sales at a Vocaloid concert cost $8 for Miku fans and $6 for Len fans, and total revenue was $480, that's the standard form equation: 8m + 6L = 480. Standard form is perfect for situations where two quantities combine to make a total. ๐ŸŽค

โœ๏ธ Worked Example โ€” Read This First!

Convert y = (3/4)x โˆ’ 2 to Standard Form (Ax + By = C).
Step-by-Step Solution
1
Clear any fractions. Multiply every term by 4 (the denominator):
4y = 3x โˆ’ 8
2
Move the x-term to the left side (subtract 3x from both sides):
โˆ’3x + 4y = โˆ’8
3
Make A positive. Multiply everything by โˆ’1:
3x โˆ’ 4y = 8
4
Check the rules: A = 3 (positive โœ“), no fractions โœ“, integers only โœ“
3x โˆ’ 4y = 8
๐Ÿ“Œ Standard Form Rules: (1) Ax + By = C  ยท  (2) A must be positive  ยท  (3) No fractions โ€” multiply through to clear them  ยท  (4) A, B, C are integers
Easy
Questions 1โ€“3 โ€” Convert slope-intercept to standard form
Question 1 EasySee Answer โ†’
Convert to Standard Form:  y = 2x + 5
Working space โ€” move x to the left, make A positive
Question 2 EasySee Answer โ†’
Convert to Standard Form:  y = โˆ’3x + 6
Working space
Question 3 EasySee Answer โ†’
Convert to Standard Form:  y = x โˆ’ 4
Working space
Medium
Questions 4โ€“8 โ€” Fractions and reverse conversions
Question 4 MediumSee Answer โ†’
Convert to Standard Form:  y = (1/2)x โˆ’ 3   (Hint: multiply everything by 2 first to clear the fraction)
Working space
Question 5 MediumSee Answer โ†’
Convert to Standard Form:  y = โˆ’(2/3)x + 4
Working space
Question 6 MediumSee Answer โ†’
Convert to Slope-Intercept Form:  2x โˆ’ 6y = 12
(This is the reverse! Isolate y.)
Working space โ€” subtract 2x, then divide every term by the coefficient of y
Question 7 MediumSee Answer โ†’
Convert to Slope-Intercept Form:  5x + 10y = 20
Working space
Question 8 MediumSee Answer โ†’
Alishba is baking. She uses apples costing $2 each and pears costing $3 each. She spends exactly $24. Write an equation in Standard Form where a = number of apples and p = number of pears.
Working space โ€” identify the two rates and the total, then write Ax + By = C
Hard
Questions 9โ€“10
Question 9 HardSee Answer โ†’
A Vocaloid concert sells student tickets for $5 and adult tickets for $10. Total ticket revenue is $200. Write an equation in Standard Form where s = student tickets and a = adult tickets. Then find and interpret the x and y intercepts.
Working space
Question 10 HardSee Answer โ†’
Which equation in standard form passes through the point (3, โˆ’1) and has a slope of 2? Show all working to verify your answer.
A)  2x โˆ’ y = 5     B)  2x โˆ’ y = 7     C)  2x + y = 7     D)  2x โˆ’ y = โˆ’7
Working space โ€” write the slope-intercept form first, then convert to standard form

๐Ÿง Baking Tip โ€” Standard Form in Recipes!

When splitting a batch: if a cookie recipe makes 24 cookies using chocolate chips (c) at $4/bag and sprinkles (s) at $2/bag, and your budget is $16, you get 4c + 2s = 16 in standard form! You can immediately find: if c=0 โ†’ s=8 bags of sprinkles max; if s=0 โ†’ c=4 bags of chocolate chips max. Those are the intercepts! Standard form helps you find the "all-or-nothing" solutions instantly. ๐Ÿช