Question

7.
Factorise the following expressions.
(i) z2 – 4z - 77​

Answer 1

Answer:

z=-7 ; z=11

Step-by-step explanation:

z²-11x+7x-77=0

z(z-11)+7(x-11)=0

(z+7)(z-11)=0

z+7=0 ; z-11=0

z=-7 ; z=11

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Answer 2

Answer:

(z- 11)(z + 7)

Step-by-step explanation:

While factorising an expression multiply the coefficients of the first and last term and break the coefficient of mid term into two numbers that add up to form the product we found out earlier.

z² - 4z - 77

( 77 × 1 = 77)

And -4z = - 11z + 7z

As 77 = 11 × 7)

=> z² - 11z + 7z - 77

Taking z common from first two terms and 7 common from the next two

=> z( z - 11) + 7(z- 11)

Taking (z - 11) common

=> (z - 11)(z + 7)

Thus is the required answer :)

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Hope this helps!