Question

1. if y varies directly with x and y = 5 when x = 4, find the value of y when x = -8.

options:
y = 1.25
y = -6.4
y = -10
y = 5.8

Explanation:

Step1: Recall direct variation formula

Direct variation is \( y = kx \), where \( k \) is the constant of variation.

Step2: Find the constant \( k \)

Given \( y = 5 \) when \( x = 4 \), substitute into \( y = kx \):
\( 5 = k \times 4 \)
Solve for \( k \): \( k=\frac{5}{4}=1.25 \)

Step3: Find \( y \) when \( x = -8 \)

Use \( y = kx \) with \( k = 1.25 \) and \( x = -8 \):
\( y = 1.25 \times (-8) \)
\( y=-10 \)

Answer:

\( y = -10 \) (corresponding to the option \( y = -10 \))