example 3
DESCRIPTION
Solve the equation for y. STEP 1. x. y =. +. –. 9. 7. 4. 4. EXAMPLE 3. Rewrite a linear equation. Solve 9 x – 4 y = 7 for y . Then find the value of y when x = –5. SOLUTION. 9 x – 4 y = 7. Write original equation. –4 y = 7 – 9 x. Subtract 9 x from each side. - PowerPoint PPT PresentationTRANSCRIPT
EXAMPLE 3 Rewrite a linear equation
Solve 9x – 4y = 7 for y. Then find the value of y when x = –5.
SOLUTION
Solve the equation for y.STEP 1
9x – 4y = 7
–4y = 7 – 9x
y = 94
74
– + x
Write original equation.
Subtract 9x from each side.
Divide each side by –4.
EXAMPLE 3 Rewrite a linear equation
Substitute the given value into the rewritten equation.
STEP 2
y = 94
74
– + (–5)
y = 454
74
– –
y = –13
CHECK
9x – 4y = 7
9(–5) – 4(–13) 7=?
7 = 7
Substitute –5 for x.
Multiply.
Simplify.
Write original equation.
Substitute –5 for x and –13 for y.
Solution checks.
EXAMPLE 4 Rewrite a nonlinear equation
Solve 2y + xy = 6 for y. Then find the value of y when x = –3.
SOLUTION
Solve the equation for y.STEP 1
2y + x y = 6
(2+ x) y = 6
y = 62 + x
Write original equation.
Distributive property
Divide each side by (2 + x).
EXAMPLE 4 Rewrite a nonlinear equation
Substitute the given value into the rewritten equation.
STEP 2
y = 62 + (–3)
y = – 6
Substitute –3 for x.
Simplify.
GUIDED PRACTICE for Examples 3 and 4
Solve the equation for y. Then find the value of y when x = 2.
8. y – 6x = 7
y = 7 + 6x
y = 19
ANSWER
9. 5y – x = 13
y = x5
135 +
y = 5
ANSWER
10. 3x + 2y = 12
y = – 3x2 + 6
ANSWER
y = 3
GUIDED PRACTICE for Examples 3 and 4
Solve the equation for y. Then find the value of y when x = 2.
11. 2x + 5y = –1 12. 3 = 2xy – x 13. 4y – xy = 28
y = 14
284 – xy =
ANSWER
y = 1
41
3 +x 2xy =
ANSWER
2x5
–15 –
y = –1
y =
ANSWER