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(Class - vil), , Exercise 12.3, Question 1:, If m = 2, find the value of:, (i) m-2 (ii) 3m-5 (iii), (iv) 3m? -2m-7 (v) my, €. Answer 1:, 0) m-2 =2-2, =0, (ii) 3m-5 = 3x2-5, =6-5=1, (ii) = 9-Sm=9-5x2, =9-10=-1, , (iv) 3m? -2m-7, = 3(2) -2(2)-7, , =3x4-2x2-7, =12-4-7, =12-11=1 fSm 5x2, Sf 4g, (vy) 2 2, =5-4=1, Question 2:, If p =-2, find the value of:, (i) 4p+7 (ii) 3p? +4p+7 (iii), €. Answer 2:, (0) 4p+7 = 4(-2)+7, =-84+7 =-1, (ii) 3p? +4p+7, = -3(-2)° +4(-2)+7, = -3x4-8+7, = -12-8+7, = -20+7 = -13, , 9-Sm, , [Putting m=2], [Putting m=2], , [Putting m=2], , [Putting m=2], , [Putting m=2], , —2p?-3p?+4p+7, , [Putting p=-2], , [Putting p=-2]

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\wrass waaay, , (iii) -2p'-3p'+4p+7, = -2(-2)'-3(-2)° +4(-2)+7 [Putting p= -2], = -2x(-8)-3x4-8+7, = 16-12-8+7, = -204+23 =3, Question 3:, Find the value of the following expressions, when x=-1:, (i) 2x-7 (ii) = -x+2 (iii) C8 +2x41, (iv) 2x? -x-2, €. Answer 3:, i) 2x-7 = 2(-1)-7 [Putting x=~1], =-2-7=-9, (ii) =x+2 = -(-1)+2 [Putting x=-I], =1+2=3, (iii) x +2x41 = (-1)°+2(-1) 41 [Putting x=-1], =1-2+1, =2-2=0, (iv) 2x? -x-2 = 2(-1)’-(-1)-2 [Putting x=-1], =2x1+1-2, =2+1-2, =3-2=1, Question 4:, If a=2,b=-2, find the value of:, (i) a+b (ii) = a? +ab+b? (iii) a? -B", €. Answer 4:, (i) a? +b? = (2) +(-2)" [Putting a= 2,b=-2], =44+4=8, (ii) a +ab+b*, = (2) +(2)(-2)+(-2)° [Putting a=2,b=-2]}, , =4-44+4=4

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(iii) a? ~b? = (2)°-(-2)° [Putting a=2,b=-2], , =4-4=0, Question 5:, When a =0,b =-1, find the value of the given expressions:, (i) 2a+2b (ii) = 2a? +57 41, (iii) 2a*b + 2ab? + ab (iv) a’ +ab+2, €. Answer 5:, i) 2a+2b = 2(0)+2(-1) [Putting a=0,b=-1], =0-2=-2, (ii) 2a? +b? +1 = 2(0) +(-1)° +1 [Putting 2=0,b=-1], , =2x04+14+1=0+2=2, (iii) -2a*b + 2ab* + ab = 2(0) (-1)+2(0)(-1)’ +(0)(-1) [Putting a =0,b=-1], , =0+0+0=0, (iv) a? +ab+2 = (0)' +(0)(-1) +2 [Putting a=0,b=-1], =0+0+2=2 /, Question 6:, Simplify the expressions and find the value if x is equal to 2:, (i) x+7+4(x-5) (ii) = 3(x+2)+5x-7, (iii) 6x+5(x-2) (iv) 4(2x-1)+3x4+11, ©. Answer 6:, (i) x+744(x-5) = x+74+4x-20 = x+4x4+7-20, = 5x-13 = 5x2-13 [Putting x=2], = 10-13 = -3, (i) 3(x+2)4+5x-7 = 3xt+64+5x-7 = 3x+5x4+6-7, = 8x-1=8x2-1 [Putting x=—1], =16-1=15, (iii) 6x+5(x-2) = 6x+5x-10 = 11x-10, =11x2-10 [Putting x=-1], =22-10=12, , Ses re

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(ii) p’ -2p-100 = (-10) -2(-10)-100 [Putting p =-10], , = 100+20-100 = 20, Question 9:, What should be the value of a if the value of 2x°+x-a equals to 5, when x=0 ?, €. Answer 9:, Given: 2x? +x-a=5, > 2(0)' +0-a=5 [Putting x=0], > 0+0-a=5, > a=-5, , Hence, the value of a is -5., , Question 10:, Simplify the expression and find its value when a=5 and b=-3: 2(a? + ab) +3-ab, € Answer 10:, Given: 2(a* +ab)+3-ab, 2a* + 2ab+3—ab, 2a* +2ab-ab+3, 2a +ab+3, 2(5)" +(5)(-3) +3 [Putting a=5, b=-3], 2x25-15+3, 50-15+3, 38, , YUU ULYUY