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MATHS [4 marks sum]

Identities · ICSE STD 8 (ICSE - English Medium). 157 questions.

Questions · Page 4 of 4

[4 marks sum]

Question 1514 Marks
Use the direct method to evaluate the following products : $(8 – b) (3 + b)$
Answer
$(8 – b) (3 + b) $
$= (8 \times 3) + (8 \times b) + (−b \times 3) + (−b \times b)= 24 + 8b − 3b − b^2$
$= 24 + 5b − b^2$
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Question 1524 Marks
Use the direct method to evaluate the following products : $(5a + 16) (3a – 7)$
Answer
$(5a + 16) (3a – 7) $
$= (5a \times 3a) + (5a \times −7) + (16 \times 3a) + 16 −7= 15a^2 + (−35a) + 48a + (−112)$
$= 15a^2− 35a + 48a − 112$
$= 15a^2 + 13a − 112$
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Question 1534 Marks
Use the direct method to evaluate the following products : $(3x – 2y) (2x + y)$
Answer
$(3x – 2y) (2x + y)$
$= (3x \times 2x) + (3x \times y) + (−2y \times 2x) + (−2y \times y)= 6x^2 + 3xy − 4xy − 2y^{2 }$
$= 6x^2 − xy − 2y^2$
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Question 1544 Marks
Use the direct method to evaluate the following products :  $(b – 3) (b – 5)$
Answer
$(b – 3) (b – 5) $
$= (b \times b) + (b \times −5) + (−3) \times b + (−3) (−5)$
$= b^2 − 5b − 3b + 15$
$= b^2− 8b + 15$
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Question 1554 Marks
Use the direct method to evaluate the following products : $(a – 8) (a + 2)$
Answer
$(a – 8) (a + 2) $
$= (a \times a) + (a \times 2) + (−8)\times a + (−8)(2)$
$= a^2+ 2a − 8a − 16$
$= a^2 − 6a − 16$
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Question 1564 Marks
Use the direct method to evaluate the following products : $(y + 5)(y – 3)$
Answer
$(y + 5) (y – 3) $
$= (y \times y) + (y \times −3) + (5 \times y) + (5 \times −3)$
$= y^2 + (−3y) + (5y) − 15$
$= y^2− 3y + 5y − 15$
$= y^2 + 2y − 15$
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Question 1574 Marks
Use direct method to evaluate the following products : $(x + 8)(x + 3)$
Answer
$ (x + 8) (x + 3)$
$= (x \times x) + (x \times 3) + (8 \times x) + (8 \times 3)$
$= x^2 + 3x + 8x + 24$
$= x^2 + 11x + 24$
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[4 marks sum] - Page 4 - MATHS STD 8 Questions - Vidyadip