Selina Concise Class 7 Math Chapter 11 Fundamental Concepts Exercise 11F Solution
EXERCISE 11F
Enclose the given terms in brackets as required:
(1) x – y – z = x – (y + z)
(2) x2 – xy2 – 2xy – y2 = x2 – (xy2 + 2xy + y2)
(3) 4a – 9 + 2b – 6 = 4a – (9 – 2b + 6)
(4) x2 – y2 + z2 + 3x – 2y = x2 – (y2 – z2 – 3x + 2y)
(5) – 2a2 + 4ab – 6a2b2 + 8ab2 = – 2a (a – 2b + 3ab2 + 4b2)
Simplify:
(6) 2x – (x + 2y – z)
= 2x – x – 2y + z
= x – 2y + z
(7) p + q – (p – q) + (2p – 3q)
= p + q – p + q + 2p – 3q
= 2q + 2p – 3q
= 2p – q
(8) 9x – (- 4x + 5)
= 9x + 4x – 5
= 13x – 5
(9) 6a – (- 5a – 8b) + (3a + b)
= 6a + 5a + 8b + 3a + b
= 14a + 9b
(10) (p – 2q) – (3q – r)
= p – 2q – 3q + r
= p – 5q + r
(11) 9a (2b – 3a + 7c)
= 18ab – 27a2 + 63ac
(12) – 5m (- 2m + 3n – 7p)
= 10m2 – 15mn + 35pm
(13) – 2x (x + y) + x2
= – 2x2 – 2xy + x2
= – x2 – 2xy
(15) 8 (2a + 3b – c) – 10 (a + 2b + 3c)
= 16a + 24b – 8c – 10a – 20b – 30c
= 6a + 4b – 38c
(17) 5x (2x + 3y) – 2x (x – 9y)
= 10x2 + 15xy – 2x2 + 18xy
= 8x2 + 33xy
(18) a + (b + c – d)
= a + b + c – d
(19) 5 – 8x – 6 – x
= – 9x – 1
(20) 2a + {b – (a – b)}
= 2a + {b – a + b}
= 2a + b – a + b
= a + 2b
(21) 3x + [4x – (6x – 3)]
= 3x + [4x – 6x + 3]
= 3x + [- 2x + 3]
= 3x – 2x + 3
= x + 3
(22) 5b – {6a + (8 – b – a)}
= 5b – {6a + 8 – b – a}
= 5b – 6a – 8 + b + a
= 6b – 5a – 8
(23) 2x – [5y – (3x – y) + x]
= 2x –[5y – 3x + y + x]
= 2x – [6y – 2x]
= 2x – 6y + 2x
= 4x – 6y
(24) 6a – 3 (a + b – 2)
= 6a – 3a – 3b + 6
= 3a – 3b + 6
(25) 8 [m + 2n – p – 7(2m – n + 3p)]
= 8 [m + 2n – p – 14m + 7n – 21p]
= 8m + 16n – 8p – 112m + 56n – 168p
= – 104m + 72n – 176p
(26) {9 – (4p – 6q)} – {3q – (5p – 10)}
= {9 – 4p + 6q} – {3q – 5p + 10}
= 9 – 4p + 6q – 3q + 5p – 10
= p + 3q – 1
(27) 2 [a – 3 {a + 5 (a – 2) + 7}]
= 2 [a – 3 {a + 5a – 10 + 7}]
= 2 [a – 3{6a – 3}]
= 2 [a – 18a + 9]
= 2 [ – 17a + 9]
= – 34a + 18
(28) 5a – [6a – {9a – (10a – (4a – 3a))}]
= 5a – [6a – 9a – (10a – a)}]
= 5a – [6a – 9a + 9a]
= 5a – [6a]
= – a
(29) 9x + 5 – [4x – {3x – 2 (4x – 3)}]
= 9x + 5 – [4x – {3x – 8x + 6}]
= 9x + 5 – [4x – {- 5x + 6}]
= 9x + 5 – [4x + 5x – 6]
= 9x + 5 – [9x – 6]
= 9x + 5 – 9x + 6
= 11
(30) (x + y – z) x + (z + x – y) y – (x + y – z) z
= x2 + xy – xz + zy + xy – y2 – xz – yz + z2
= x2 – y2 + z2 + 2xy – 2xz
(31) – 1 [a – 3 {b – 4 (a – b – 8) + 4a} + 10]
= – 1[a – 3 {b – 4a + 4b + 32 + 4a} + 10]
= – 1[a – 3 {5b + 32} + 10]
= – 1 [a – 15b – 96 + 10]
= – 1 [a – 15b – 86]
= – a + 15b + 86
(32) p2 – [x2 – {x2 – (q2 – (x2 – q2) – 2y2}]
= p2 – [x2 – {x2 – (q2 – x2 – q2 – 2y2]
= p2 – [x2 – {x2 – q2 + x2 – q2 – 2y2]
= p2 – [x2 – x2 + q2 – x2 + q2 + 2y2]
= p2 – [2q2 – x2 + 2y2]
= p2 – 2q2 + x2 – 2y2
(33) 10 – [4a – {7 – (a – 5)} – {5a – (1 + a)}]
= 10 – [4a – {7 – a + 5} – {5a – 1 – a}]
= 10 – [4a – {12 – a} – {4a – 1}]
= 10 – [4a – 12 + a – 4a + 1]
= 10 – [a – 11]
= 10 – a + 11
= 21 – a
(34) 7a – [8a – {11a – (12a – (6a – 5a))}]
= 7a – [8a – {11a – (12a – 6a + 5a)}]
= 7a – [8a – {11a – (12a – a)}]
= 7a – [8a – {11a – 11a}]
= 7a – [8a – 11a + 11a]
= 7a – 8a
= – a
(35) 8x – [4y – {4x + (2x – (2y – 2x))}]
= 8x – [4y – {4x + (2x – 2y + 2x)}]
= 8x – [4y – {4x + 4x – 2y}]
= 8x – [4y – 8x + 2y]
= 8x – [6y – 8x]
= 8x – 6y + 8x
= 16x – 6y
(36) x – {3y – (4z – 3x) + 2z – (5y – 7x)}
= x – {3y – 4z + 3x + 2z – 5y + 7x}
= x – {- 2y – 2z + 10x}
= x + 2y + 2z – 10x
= – 9x + 2y + 2z
the solution helped me so much
The solution helped me so much.
help very much