S.chand books class 8 maths solution chapter 12 Fundamental concept and Operations exercise 12 B

 EXERCISE 12 B

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Q1 | Ex-12B | Class-8 | Schand Composite Mathematics | Fundamental concept and operations | myhelper

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QUESTION 1

Add the following expressions

(i) 2ab+3b and 5ab+7b

Sol:  

=2ab+3b+5ab+7b

=2ab+3b+5ab+7b

=7ab+10b

(ii) 2x²+3xy and 6xy-4x²

Sol :

=2x²+3xy+6xy-4x²

=2x²-4x²+3xy+6xy

=-2x²+9xy

(iii) 5z²-11z+7 and 10z²-18+7z

Sol :

=5z²-11z+7+10z²-18+7z

=5z²+10z²-11z+7z+7-18

=15z²-4z-11

(iv) y³-3y²+7y-17 and 2y²-5y-8y³+20

Sol :

=y³-3y²+7y-17+2y²-5y-8y³+20

=y³-8y³-3y²+2y²+7y-5y-17+20

=7y³-y²+2y+3

(v) 4x²-7xy+8z and x²-2xy+9z and -3x²+8xy

Sol :

=4x²-7xy+8z+x²-2xy+9z-3x²+8xy

=4x²+x²-3x²-7xy-2xy+8xy+8z+9z

=2x²-xy+17z

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Q2 | Ex-12B | Class-8 | Schand Composite Mathematics | Fundamental concept and operations | myhelper

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QUESTION 2

Subtracted as indicated :

(i) (4a-5b-c)-(3a+2b-7c)

Sol :

=(4a-5b-c)-(3a+2b-7c)

=4a-5b-c-3a-2b+7c

=4a-3a-5b-2b-c+7c

=a-7b+6c

(ii) 4x²-5x+3 from 4x²-3x+2

Sol :

=(4x²-3x+2)-(4x²-5x+3)

=4x²-3x+2-4x²+5x-3

=4x²-4x²-3x+5x+2-3

=2x-1

(iii) 4xy-8+y² from 5x²+6xy-6

Sol :

=(5x²+6xy-8)-(4xy-6+y²)

=5x²+6xy-8-4xy+6-y²

=5x²-y²+6xy-4xy-8+6

=5x²-y²+2xy-2

(iv) (-4x²-x+9)-(3x²-x)

Sol :

=-4x²-x+9-3x²+x

=-4x²-3x²-x+x+9

=-7x²+9

 

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Q3 | Ex-12B | Class-8 | Schand Composite Mathematics | Fundamental concept and operations | myhelper

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QUESTION 3

From the sum of x+3y and -3x-y subtract x-y

Sol :

=[x+3y-3x-y]-(x-y)

=[x-3x+3y-y]-(x-y)

=-2x+2y-x+y

=-2x-x+2y+y

=-3x+3y

 

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Q4 | Ex-12B | Class-8 | Schand Composite Mathematics | Fundamental concept and operations | myhelper

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QUESTION 4

Subtract a²-b²-c² from the sum of 2a²+3b²-c² and 4a²-3b²+5c²

Sol :

=(2a²+3b²-c²+4a²-3b²+5c²)-(a²-b²-c²)

=(2a²+4a²+3b²-3b²-c²+5c²)-a²+b²+c²

=(6a²+4c²)-a²+b²+c²

=6a²+4c²-a²+b²+c²

=6a²-a²+4c²+c²+b²

=5a²+5c²+b²

 

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Q5 | Ex-12B | Class-8 | Schand Composite Mathematics | Fundamental concept and operations | myhelper

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QUESTION 5

Subtract the sum of (4x³+2x²-5) and (15x-x³-x²) from the sum of (9+6x-2x²) and (4x-1-5x³+x²)

Sol :

=[(9+6x-2x²) and (4x-1-5x³+x²)-(4x³+2x²-5) and (15x-x³-x²)]

=[(9+6x-2x²+4x-1-5x³+x²)-(4x³+2x²-5+15x-x³-x²)]

=[(-5x³-2x²+x²+4x+6x-1+9)-(4x³-x³+2x²-x²+15x-5)]

=[(-5x³-x²+10x+8)-(3x³+x²+15x-5)]

=-5x³-x²+10x+8-3x³-x²-15x+5

=-5x³-3x³-x²-x²+10x-15x+8+5

=-8x³-2x²-5x+13

 

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