Chapter 4
Exploring Algebraic Identities
CBSE Class 9
Mathematics Solutions
Educart Mathematics class Class 9 NCERT Exemplar cover
Question:

Fill in the blanks to complete the following identities:

(A) s2−11s+24=(‾)(‾)s^2 - 11s + 24 = (\underline{\hspace{2cm}})(\underline{\hspace{2cm}})

(B) (‾)(x+1)=3x2−4x−7(\underline{\hspace{2cm}})(x + 1) = 3x^2 - 4x - 7

(C) 10x2−11x−6=(2x−‾)(‾+2)10x^2 - 11x - 6 = (2x - \underline{\hspace{2cm}})(\underline{\hspace{2cm}} + 2)

(D) 6x2+7x+2=(‾)(‾)6x^2 + 7x + 2 = (\underline{\hspace{2cm}})(\underline{\hspace{2cm}})

Answer: Verified

(A) Use a+b=−11,ab=24a + b = -11, ab = 24

So, a=−3,b=−8\text{So, } a = -3, b = -8

s2−11s+24=s2−3s−8s+24s^2 - 11s + 24 = s^2 - 3s - 8s + 24

=(s−3)(s−8)= (s - 3)(s - 8)

(B) Divide 3x2−4x−73x^2 - 4x - 7 by (x+1)(x + 1):

3x2−4x−7=3x2+3x−7x−7=3x(x+1)−7(x+1)=(3x−7)(x+1)\begin{aligned} 3x^2 - 4x - 7 &= 3x^2 + 3x - 7x - 7 \\ &= 3x(x + 1) - 7(x + 1) \\ &= (3x - 7)(x + 1) \end{aligned}

(3x−7)(x+1)=3x2−4x−7(3x - 7)(x + 1) = 3x^2 - 4x - 7

(C) Split −11x-11x using factors of 10×(−6)=−6010 \times (-6) = -60:

−15+4=−11 and −15×4=−60-15 + 4 = -11 \text{ and } -15 \times 4 = -60

10x2−11x−6=10x2−15x+4x−6=5x(2x−3)+2(2x−3)=(2x−3)(5x+2)\begin{aligned} 10x^2 - 11x - 6 &= 10x^2 - 15x + 4x - 6 \\ &= 5x(2x - 3) + 2(2x - 3) \\ &= (2x - 3)(5x + 2) \end{aligned}

(D) Split 7x7x using factors of 12:

3+4=7,3×4=126x2+7x+2=6x2+3x+4x+2=3x(2x+1)+2(2x+1)=(2x+1)(3x+2)\begin{aligned} 3 + 4 &= 7, 3 \times 4 = 12 \\ 6x^2 + 7x + 2 &= 6x^2 + 3x + 4x + 2 \\ &= 3x(2x + 1) + 2(2x + 1) \\ &= (2x + 1)(3x + 2) \end{aligned}

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