ICSE Class 10 Maths Selina Solutions Chapter 8: ICSE Class 10 Maths Selina Solutions for Chapter 8 Remainder and Factor Theorems provide a detailed guide to understanding and applying these crucial algebraic concepts.
With clear step-by-step explanations and examples these solutions simplify complex problems, making it easier for students to solve them accurately. By practicing these solutions students can enhance their problem-solving skills and build a strong foundation in algebra which is important for their academic success in mathematics.ICSE Class 10 Maths Selina Solutions Chapter 8 PDF
1. Show that (x – 1) is a factor of x 3 – 7x 2 + 14x – 8. Hence, completely factorise the given expression.
Solution:
Let f(x) = x 3 – 7x 2 + 14x – 8 Then, for x = 1 f(1) = (1) 3 – 7(1) 2 + 14(1) – 8 = 1 – 7 + 14 – 8 = 0 Thus, (x – 1) is a factor of f(x). Now, performing long division we have2. Using Remainder Theorem, factorise:
x 3 + 10x 2 – 37x + 26 completely.
Solution:
Let f(x) = x 3 + 10x 2 – 37x + 26 From remainder theorem, we know that For x = 1, the value of f(x) is the remainder f(1) = (1) 3 + 10(1) 2 – 37(1) + 26 = 1 + 10 – 37 + 26 = 0 As f(1) = 0, x – 1 is a factor of f(x). Now, performing long division we have3. When x 3 + 3x 2 – mx + 4 is divided by x – 2, the remainder is m + 3. Find the value of m.
Solution:
Let f(x) = x 3 + 3x 2 – mx + 4 From the question, we have f(2) = m + 3 (2) 3 + 3(2) 2 – m(2) + 4 = m + 3 8 + 12 – 2m + 4 = m + 3 24 – 3 = m + 2m 3m = 21 Thus, m = 74. What should be subtracted from 3x 3 – 8x 2 + 4x – 3, so that the resulting expression has x + 2 as a factor?
Solution:
Let’s assume the required number to be k. And let f(x) = 3x 3 – 8x 2 + 4x – 3 – k From the question, we have f(-2) = 0 3(-2) 3 – 8(-2) 2 + 4(-2) – 3 – k = 0 -24 – 32 – 8 – 3 – k = 0 -67 – k = 0 k = -67 Therefore, the required number is -67.5. If (x + 1) and (x – 2) are factors of x 3 + (a + 1)x 2 – (b – 2)x – 6, find the values of a and b. And then, factorise the given expression completely.
Solution:
Let’s take f(x) = x 3 + (a + 1)x 2 – (b – 2)x – 6 As, (x + 1) is a factor of f(x). Then, remainder = f(-1) = 0 (-1) 3 + (a + 1)(-1) 2 – (b – 2) (-1) – 6 = 0 -1 + (a + 1) + (b – 2) – 6 = 0 a + b – 8 = 0 … (1) And as, (x – 2) is a factor of f(x). Then, remainder = f(2) = 0 (2) 3 + (a + 1) (2) 2 – (b – 2) (2) – 6 = 0 8 + 4a + 4 – 2b + 4 – 6 = 0 4a – 2b + 10 = 0 2a – b + 5 = 0 … (2) Adding (1) and (2), we get 3a – 3 = 0 Thus, a = 1 Substituting the value of a in (i), we get, 1 + b – 8 = 0 Thus, b = 7 Hence, f(x) = x 3 + 2x 2 – 5x – 6 Now as (x + 1) and (x – 2) are factors of f(x). So, (x + 1) (x – 2) = x 2 – x – 2 is also a factor of f(x).6. If x – 2 is a factor of x 2 + ax + b and a + b = 1, find the values of a and b.
Solution:
Let f(x) = x 2 + ax + b Given, (x – 2) is a factor of f(x). Then, remainder = f(2) = 0 (2) 2 + a(2) + b = 0 4 + 2a + b = 0 2a + b = -4 … (1) And also given that, a + b = 1 … (2) Subtracting (2) from (1), we have a = -5 On substituting the value of a in (2), we have b = 1 – (-5) = 67. Factorise x 3 + 6x 2 + 11x + 6 completely using factor theorem.
Solution:
Let f(x) = x 3 + 6x 2 + 11x + 6 For x = -1, the value of f(x) is f(-1) = (-1) 3 + 6(-1) 2 + 11(-1) + 6 = -1 + 6 – 11 + 6 = 12 – 12 = 0 Thus, (x + 1) is a factor of f(x).8. Find the value of ‘m’, if mx 3 + 2x 2 – 3 and x 2 – mx + 4 leave the same remainder when each is divided by x – 2.
Solution:
Let f(x) = mx 3 + 2x 2 – 3 and g(x) = x 2 – mx + 4 From the question, it’s given that f(x) and g(x) leave the same remainder when divided by (x – 2). So, we have: f(2) = g(2) m(2) 3 + 2(2) 2 – 3 = (2) 2 – m(2) + 4 8m + 8 – 3 = 4 – 2m + 4 10m = 3 Thus, m = 3/10