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Big Ideas Math Integrated I, 2016

BI

Big Ideas Math Integrated I, 2016 View details

2. Solving Systems of Linear Equations by Substitution

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Exercise 17 Page 227

Into which equation should we substitute the isolated expression of y?

Error: Substitution made into incorrect equation.
Correct Answer: x=- 2/9

Practice makes perfect

In the first step, no mistakes have been made. Moving on to the second step, the expression for y should be substituted into the other equation to calculate x. Not the same equation! Let's complete the second step properly.

8x+2y=- 12

y= 5x-4

8x+2( 5x-4)=- 12

▼

Solve for x

Distribute 2

8x+10x-4=- 12

Add terms

18x-8=- 12

LHS+8=RHS+8

18x=- 4

.LHS /18.=.RHS /18.

x=- 4/18

MoveNegNumToFrac

Put minus sign in front of fraction

x=- 4/18

a/b=.a /2./.b /2.

x=- 2/9

The value of x is - 29.

Subchapter links

Communicate Your Answer p.223

Monitoring Progress p.224-226

Exercises p.227-228