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CHAPTER1.5T
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à 1.5ïVariables, Expressions, & Equations.
äïPlease find the numerical value of the following algebraic
expressions by substituting the given value of the variable.
â
êêêèx + 3 at x = 4,ï4 + 3 = 7
éS
è To find the numerical value of an algebraic expression such as
è 2x + 3y - 2, substitute the numerical values of the variable that
è are given and then simplify.
êêê2x + 3y - 2 at x = 5 and y = 4
êêêë 2 ∙ 5 + 3 ∙ 4 - 2
êêêë 10è+ï12è - 2
êêêë 22êë- 2
êêêêê20
1
êêêêêêêêèå
ëx + 7 at x = 5,ï?êA) 10è B) 12è C) 2è D)ïof
êêêêêêêêèç
ü
êêêëx + 7 = 5 + 7 = 12
Ç B
2
êêêêêêêêè å
ë5 ∙ xïat x = 2,ï?êA) 3ëB) 10è C) 7è D)ïof
êêêêêêêêè ç
ü
êêêë5 ∙ x = 5 ∙ 2 = 10
Ç B
3
êêêêêêêêè å
è 2x - 1ïat x = 3,ï?êA) 8ëB) 4ëC) 5è D)ïof
êêêêêêêêè ç
ü
êêêë2x - 1 = 6 - 1 = 5
Ç C
4
êïx + 4êêë5ê 8êêïå
#ê ───────ïat x = 2,è A) ─ëB) ─ëC) 2è D)ïof
êè 3êêê3ê 3êêïç
ü
êêêïx + 4ë 2 + 4ë6
#êêê ───────ï=ï─────ï=ï─ï=ï2
êêêè 3êè3ê3
Ç C
5
ê 4x - 3êêë23êêï17ë å
#ê ───────ïat x = 5,è A) ──è B) -1è C) ──èD)ïof
êè2xêêê10êêï10ë ç
ü
êêè4x - 3ë 4 ∙ 5 - 3è 20 - 3ë17
#êêè───────ï=ï─────────ï= ──────ï=ï──
êêè 2 ∙ xê 2 ∙ 5ê 10ê10
Ç C
6
êêêêêêêêè å
#è 3x + xì at x = 3,ï?êA) 36è B) 18è C) 12èD)ïof
êêêêêêêêè ç
ü
#êêë3x + xì =ï3 ∙ 3 + 3ìï=ï9 + 9ï=ï18
Ç B
7
êêêêêêêêë å
#ë.23xì at x = 2,ï?ê A) 9.2èB) .92èC) .092èD)ïof
êêêêêêêêë ç
ü
#êêê.23xì = .23(2)ì = .23(4) = .92
Ç B
äïPlease find the numerical value of the following algebraic
expressions in two variables by substituting the values of x and y
â
êë 2x + 3y; at x = 2 and y = 4,ë2 ∙ 2 + 3 ∙ 4 = 16
éS
èTo find the numerical value of an algebraic expression such as
è2x + 3y - 2, substitute the numerical values of the variable that
èare given and then simplify.
êêë 2x + 3y - 2 at x = 5 and y = 4
êêêë 2 ∙ 5 + 3 ∙ 4 - 2
êêêë 10è+ï12è - 2
êêêë 22êë- 2
êêêêë 20
8
êêêêêêêêêè å
3x + 5y + 6; at x=1 & y=2, ?ê A) 36è B) 19è C) 43ëD)ïof
êêêêêêêêêè ç
ü
êï3x + 5y + 6;ë3 ∙ 1 + 5 ∙ 2 + 6ï=ï3 + 10 + 6ï=ï19
êêêêat x=1 and y=2
Ç B
9
êêêêêêêêê å
4(x + 3y); at x=3 and y=2,ï?è A) 72è B) 18è C) 36ëD)ïof
êêêêêêêêê ç
ü
ë4(x + 3y); at x=3 & y=2,è4(3 + 3 ∙ 2) = 4(3 + 6) = 4(9) = 36
Ç C
10
ê 4x - 2yêêè 22ê2ê 10ë å
#ê───────── at x = 4ëA) ──è B) ─ëC) ──èD)ïof
êx + y + 2è y = 3,ê 9ê9êï9ë ç
ü
êê 4x - 2yê 4∙4 - 2∙3è 16 - 6ë10
#êê─────────è =ï─────────ï= ──────ï=ï──
êêx + y + 2ê4 + 3 + 2ê9ê 9
Ç C
äïPlease substitute the given value of the variable into
the equation and decide whether it is a solution of the equation.
â
êêè2x + 3 = 7;ïat x=2,ï2 ∙ 2 + 3 = 7èYES
éS
To determine if a given number is a solution of an equation, substitute
the number for the variable in the equation and see if a true sentence
results.
#ï2x + 4 = 12; x = 3èsince 2 ∙ 3 + 4 ╪ 12, 3 is not a solution to
êêêêêêëthe equation 2x + 4 = 12
ï2x + 4 = 12, x = 4èsince 2 ∙ 4 + 4 = 12 is a true sentence, 4 is a
êêêêêêïsolution of 2x + 4 = 12
11
êêx - 6 = 14; at x=20ï?ê A) YESèB) NO
ü
êêè x - 6 = 14; at x=20,ï20 - 6 = 14ïYES
Ç A
12
êë 5x + 4 = 12; at x=2è?ê A) YESèB) NO
ü
#êêè 5x + 4 = 12; at x=2 ,ï5 ∙ 2 + 4 ƒ 12
Ç B
13
êè 3a + 4(a + 5) = 20; at a=1è?ê A) YESèB) NO
ü
#êï3a + 4(a + 5) = 20; at a=1è3 ∙ 1 + 4(1 + 5) ƒ 20èNO
Ç B
14
#êê 4rì - 2 = 34; at r=3è?ê A) YESèB) NO
ü
#êè4rì - 2 = 34; at r=3,ï4 ∙ 3ì - 2,è4 ∙ 9 - 2 = 2ïYES
Ç A
15
êêïx + 4è7êï2
#êêï───── = ─; at x = ─è?ê A) YESèB) NO
êêï2 - xè2êï3
üêêêè2
#êêêêï─ + 4
êêë x + 4ë3êï7
#êêë ─────ï=ï─────ï=ï─êYES
êêë 2 - xêï2ë2
#êêêêï2 - ─
êêêêë 3
Ç A