# NCTB Class 6 Math Chapter Four Exercise 4.2 Solution

NCTB Class 6 Math Chapter Four Exercise 4.2 Solution by Math Expert. Bangladesh Board Class 6 Math Solution Chapter 4 “Algebraic Expressions’’ Exercise 4.2 Solution.

 Board NCTB Class 6 Subject Mathematics Chapter 4 Chapter Name “Algebraic Expressions’’ Exercise 4.2 Solution

### Exercise:- 4.2

(1) Simplify:

Solution:-

(i) x3 X x7

= x10

(ii) a3 x a x a5

= a9

(iii) x4 X x2X x9

=x15

(iv) m x m2 x n3 x m3 x n7

=m6 n10

(v) 3a x 4b x2a x 5c x3b

= 360 a2 b2 c

(vi) 2x2 X y2 X 2z2 X 3y2 X 4x2

= 48 x4 y4 z2

(2) If a=2, b=3, c=1, find the value of each of the following expressions:

Solution:-

(i) a3 + b2

= (2)2+ (3)2

= 8+27

= 35          [Therefore a=2; b=3]

(ii) b + c

= 27+1

= 28

(iii) a2–b2 +c2

= (2)2 – (3)2 + (1)2

= 4-9+1

= -5+1

= -4

(iv) b2– 2ab+a2

= (3)2 – 2X2X3+ (2)2

= 9-12+4

= -3+4

= 1

(v) a2 -2ac+c2

= (2)2 – 2X2X1+12

= 4-4+1

= 1

(3) If x=3, y=5, z=2, show that

Solution:-

Therefore, L.H.S,  y2-x2

= (y+x) (y-x)

= (5+3) (5-3)

= 8×2

= 16

R.H.S,  (x+y) (y-x)

= (3+5) (5-3)

= 8×2

= 16

Therefore, L.H.S= R.H.S (proved)

(ii) L.H.S, (x+y)2

= x 2+ 2xy+y2

= (3)2 + 2x3x5 +52

= 9+30+25

= 64

R.H.S, (x-y) + 4xy

= (x+y)2

= (3+5)2

= (8)2

= 64

Therefore, L.H.S = R.H.S (proved)

(iii) L.H.S, (y+z)2

= (5+2)2

= (7)2

= 49

R.H.S, y+2xz+z

= 52 +2x5x2+22

= 25+20+4

= 49

Therefore, L.H.S= R.H.S (proved)

(iv) L.H.S, (x+z)2

= (3+2)2

= (5)2

= 25

R.H.S, x+2xz+z

= 32+2x3x2+22

= 9+12+4

= 25

Therefore, L.H.S= R.H.S (proved)

Solution:-

(i) a7x a8

= a15 (b)

(ii) a3 x a-3

= a0(c)

(iii) 5x2 X 4x4

= 20x6 (b)

(iv) x5X x4

= x9

(v) 5a3X a5

= 5a8

Updated: December 4, 2020 — 8:49 am