NCERT Class-8 Maths Factorisation Chapter-14.4
Find and correct the errors in the following mathematical statements:
Question 1: 4(x – 5) = 4x – 5
Question 2: x(3x + 2) = 3x2 + 2
Question 3: 2x + 3y = 5xy
Question 4: x + 2x + 3x = 5x
Question 5: 5y + 2y + y – 7y = 0
Question 6: 3x + 2x = 5x2
Question 7: (2x)2 + 4(2x) + 7 = 2x2 + 8x + 7
Question 8: (2x)2 + 5x = 4x + 5x = 9x
Question 9: (3x + 2)2 = 3x2 + 6x + 4
1 Answers
Question 1: 4(x – 5) = 4x – 5
Answer: 4(x – 5) = 4x – 20
Question 2: x(3x + 2) = 3x2 + 2
Answer: = 3x2 + 2x
Question 3: 2x + 3y = 5xy
Answer: 2x + 3y
Here; x and y are as different as chalk and cheese and hence cannot be added together.
Question 4: x + 2x + 3x = 5x
Answer: = 6x
It is like adding one apple, two apples and three apples.
Question 5: 5y + 2y + y – 7y = 0
Answer: = y
Question 6: 3x + 2x = 5x2
Answer: = 5x
Question 7: (2x)2 + 4(2x) + 7 = 2x2 + 8x + 7
Answer: = 4x2 + 8x + 7
Question 8: (2x)2 + 5x = 4x + 5x = 9x
Answer: 4x2 + 5x
Question 9: (3x + 2)2 = 3x2 + 6x + 4
Answer: Using (a + b)2 = a2 + 2ab + b2;
= 9x2 + 12x + 4