第6章代数表达式和恒等式–练习6.3 |套装1
以单项式解释每种产品,并在每种情况下针对x = 1验证结果
问题18: (3x)*(4x)*(-5x)
解决方案:
First, separate the numbers and variables.
= (3 * 4 * -5) * (x * x * x)
Add the powers of the same variable and multiply the numbers.
= (-60) * (x1+1+1)
= -60x3
Verification:
LHS = (3x) * (4x) * (-5x)
Putting x = 1 in LHS we get,
= (3 * 1) * (4 * 1) * (-5 * 1)
= 3 * 4 * -5
= -60
RHS = -60x3
Putting x = 1 in RHS we get,
= -60 * (1)3
= -60
LHS = RHS
Hence, verified.
问题19: (4x 2 )*(-3x)*((4/5)x 3 )
解决方案:
First separate the numbers and variables.
= (4 * -3 * (4/5)) * (x2 * x * x3)
Add the powers of the same variable and multiply the numbers.
= (-48/5) * (x2+1+3)
= (-48/5)x6
Verification:
LHS = (4x2) * (-3x) * ((4/5)x3)
Putting x = 1 in LHS we get,
= (4 * 1) * (-3 * 1) * ((4/5) * 1)
= 4 * -3 * (4/5)
= (-48/5)
RHS = (-48/5)x6
Putting x = 1 in RHS we get,
= (-48/5) * (1)6
= -(48/5)
LHS = RHS
Hence, verified.
问题20: (5x 4 )*(x 2 ) 3 *(2x) 2
解决方案:
First separate the numbers and variables.
= (5 * 4) * (x4 * x6 * x2)
Add the powers of the same variable and multiply the numbers.
= (20) * (x4+6+2)
= (20)x12
Verification:
LHS = (5x4) * (x2)3 * (2x)2
Putting x = 1 in LHS we get,
= (5 * (1)4) * ((12))3 * (2 * 1)2
= (5 * 1) * (1)3 * (2)2
= 5 * 1 * 4
= 20
RHS = (20)x12
Putting x = 1 in RHS we get,
= (20) * (1)12
= 20
LHS = RHS
Hence, verified.
问题21: (x 2 ) 3 *(2x)*(-4x)*(5)
解决方案:
First separate the numbers and variables.
= (2 *-4 * 5) * (x6 * x * x)
Add the powers of the same variable and multiply the numbers.
= (-40) * (x6+1+1)
= (-40)x8
Verification:
LHS = (x2)3 * (2x) * (-4x) * (5)
Putting x = 1 in LHS we get,
= (1)6 * (2 * 1) * (-4 * 1) * (5)
= 1 * 2 * -4 * 5
= -40
RHS = (-40)x8
Putting x = 1 in RHS we get,
= (-40) * (1)8
= -40
LHS = RHS
Hence, verified.
问题22:记下-8x 2 y 6和-20xy的乘积。验证乘积x = 2.5,y = 1。
解决方案:
(-8x2y6 ) * (-20xy)
First separate the numbers and variables.
= (-8 * -20) * (x2 * x) * (y6 * y)
Add the powers of the same variable and multiply the numbers.
= 160 * (x2+1) * (y6+1)
= 160x3y7
Verification:
LHS = (-8x2y6) * (-20xy)
Putting x = 2.5 and y = 1 in LHS we get,
= (-8 * (2.5)2 * (1)6) * (-20 * 2.5 * 1)
= (-8 * 6.25 * 1) * (-20 * 25)
= -50 * -50
= 2500
RHS = 160x3y7
Putting x = 2.5 and y = 1 in RHS we get,
= -160 * (2.5)3 * (1)7
= -160 * 15.625
= 2500
LHS = RHS
Hence, verified.
问题23:当x = 1且y = 0.5时,评估(3.2x 6 y 3 )*(2.1x 2 y 2)。
解决方案:
First, separate the numbers and variables.
= (3.2 * 2.1) * (x6 * x2) * (y3 * y2)
Add the powers of the same variable and multiply the numbers.
= 6.72 * (x6+2) * (y3+2)
= 6.72x8y5
Putting x = 1 and y = 0.5 in the result we get
= 6.72 * (1)8 * (0.5)5
= 6.72 * 0.03125
= 0.21
问题24:当x = 1,y = 0.5时,求出(5x 6 )*(-1.5x 2 y 3 )*(-12xy 2)的值。
解决方案:
First, separate the numbers and variables.
= (5 * -1.5 * -12) * (x6 * x2 * x) * (y3 * y2)
Add the powers of the same variable and multiply the numbers.
= 90 * (x6+2+1) * (y3+2)
= 90x9y5
Putting x = 1 and y = 0.5 in the result we get
= 90 * (1)9 * (0.5)5
= 90 * 1 * 0.03125
= 2.8125
问题25:当a = 1和b = 0.5时评估(2.3a 5 b 2 )*((1.2)a 2 b 2)的时间。
解决方案:
First, separate the numbers and variables.
= (2.3 * 1.2) * (a5 * a2) * (b2 * b2)
Add the powers of the same variable and multiply the numbers.
= 2.76 * (a5+2) * (b2+2)
= 2.76a7b4
Putting a = 1 and b = 0.5 in the result we get
= 2.76 * (1)7 * (0.5)4
= 2.76 * 1 * 0.0625
= 0.1725
问题26:当x = 2.5且y = 1时评估(-8x 2 y 6)*(-20xy)
解决方案:
First, separate the numbers and variables.
= (-8 * -20) * (x2 * x) * (y6 * y)
Add the powers of the same variable and multiply the numbers.
= 160 * (x2+1) * (y6+1)
= 160x3y7
Putting x = 2.5 and y = 1 in the result we get
= 160 * (2.5)3 * (1)7
= 160 * 15.625 * 1
= 2500
将以下每个产品表示为单项式,并验证x = 1,y = 2的结果:(27 – 31)
问题27:(-xy 3 )*(yx 3 )*(xy)
解决方案:
First separate the numbers and variables.
= (-1 * 1 * 1) * (x * x3 * x) * (y3 * y * y)
Add the powers of the same variable and multiply the numbers.
= -1 * (x1+3+1 ) * (y3+1+1)
= -x5y5
Verification:
LHS = (-xy3) * (yx3) * (xy)
Putting x = 1 and y = 2 in LHS we get,
= (-1 * (2)3) * (2 * (1)3 ) * (1 * 2)
= -8 * 2 * 2
= -32
RHS = -x5y5
Putting x = 1 and y = 2 in RHS we get,
= -1 * (1)5 * (2)5
= -32
LHS = RHS
Hence, verified.
问题28: ((1/8)x 2 y 4 )*((1/4)x 4 y 2 )*(xy)*(5)
解决方案:
First, separate the numbers and variables.
= ((1/8) * (1/4) * 1 * 5) * (x2 * x4 * x) * (y4 * y2 * y)
Add the powers of the same variable and multiply the numbers.
= (5/32) * (x2+4+1) * (y4+2+1)
= (5/32)x7 y7
Verification:
LHS = ((1/8) x2y4) * ((1/4) x4y2) * (xy) * (5)
Putting x = 1 and y = 2 in LHS we get,
= ((1/8) * (1)2 * (2)4) * ((1/4) * (1)4 * (2)2) * (1 * 2) * (5)
= 2 * 1 * 2 * 5
= 20
RHS = (5/32)x7y7
Putting x = 1 and y = 2 in RHS we get,
= (5/32) * (1)7 * (2)7
= (5/32) * (128)
= 20
LHS = RHS
Hence, verified
问题29: (2/5)a 2 b *(-15b 2 ac)*((-1/2)c 2 )
解决方案:
First, separate the numbers and variables.
= ((2/5) * (-15) * (-1/2)) * (a2 * a) * (b* b2) * (c * c2)
Add the powers of the same variable and multiply the numbers.
= 3 * (a2+1) * (b1+2 ) * (c1+2)
= 3a3b3c3
This expression does not contain x and y . Hence the result cannot be verified for x = 1 and y = 2.
问题30:((-4/7)a 2 b)*((-2/3)b 2 c)*((-7/6)c 2 a)
解决方案:
First separate the numbers and variables.
= ((-4/7) * (-2/3) * (-7/6)) * (a2 * a) * (b* b2) * (c * c2)
Add the powers of the same variable and multiply the numbers.
= (-4/9) * (a2+1) * (b1+2) * (c1+2)
= (-4/9)a3b3c3
This expression does not contain x and y . Hence the result cannot be verified for x = 1 and y = 2.
问题31: ((4/9)abc 3 )*((–27 / 5)a 3 b 2 )*(-8b 3 c)
解决方案:
First, separate the numbers and variables.
= ((4/9) * (-27/5) * (-8)) * (a * a3) * (b * b2 * b3) * (c3 * c)
Add the powers of the same variable and multiply the numbers.
= (96/5) * (a1+3) * (b1+2+3) * (c3+1)
= (96/5)a4b6c4
This expression does not contain x and y. Hence, the result cannot be verified for x = 1 and y = 2.
当x = 2和y = -1时,请评估以下各项。
问题32: (2xy)*((x 2 y)/ 4)*(x 2 )*(y 2 )
解决方案:
First, separate the numbers and variables.
= (2 * (1/4)) * (x * x2 * x2) * (y * y * y2)
Add the powers of the same variable and multiply the numbers.
= (1/2) * (x1+2+2) * (y1+1+2)
= (1/2)x5y4
Putting x = 2 and y = -1 in the result we get,
= (1/2) * ( 2)5 * (-1)4
= 16
问题33: (3/5)x 2 y *((-15/4)* x * y 2 )*((7/9)x 2 y 2 )
解决方案:
First, separate the numbers and variables.
= ((3/5) * (-15/4) * (7/9)) * (x2 * x * x2) * (y * y2 * y2)
Add the powers of the same variable and multiply the numbers.
= (-7/4) * (x2+1+2) * (y1+2+2)
= (-7/4)x5y5
Putting x = 2 and y = -1 in the result we get,
= (-7/4) * ( 2)5 * (-1)5
= -56