Exercise 38 Page 172

When using the Substitution Method to solve a system of equations, it is necessary to isolate a variable.

(72/10,216/10,144/10)

Practice makes perfect

The given system consists of equations of planes. We will use the Substitution Method to solve this system because in the second and the third equations there are isolated variables. The first step will be to substitute the values of l and h into the first equation and solve for w.

2l+2w+h=72 l=3w h=2w

SubstituteII

(I): l= 3w, h= 2w

2( 3w)+2w+ 2w=72 l=3w h=2w

▼

(I):Solve for w

Multiply

(I):Multiply

6w+2w+2w=72 l=3w h=2w

AddTerms

(I):Add terms

10w=72 l=3w h=2w

DivEqn

(I):.LHS /10.=.RHS /10.

w= 7210 l=3w h=2w

The value of w is 7210. Substituting 7210 for w into the second and the third equations, we can find the values of l and h.

w= 7210 l=3w h=2w

(II), (III): w= 7210

w= 7210 l=3( 7210) h=2( 7210)

(II), (III): a*b/c= a* b/c

w= 7210 l= 3(72)10 h= 2(72)10

(II), (III): Multiply

w= 7210 l= 21610 h= 14410

The solution to the system is the point ( 7210, 21610, 14410). This is the singular point at which all three planes intersect.

Subchapter links

Lesson Check p.171

Practice and Problem-Solving Exercises p.171-173

Standardized Test Prep p.173

Mixed Review p.173

Exercise 38 Page 172

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