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12. Factorisation
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Q1 of 105 Page 280

Find the errors and correct the following mathematical sentences

Substitute x = – 3 in


(a) x2 + 7x + 12 = (–3)2 + 7 (–3) + 12 = 9 + 4 + 12 = 25

If LHS is


x2 + 7x + 12


Then RHS would be


⇒ x2 + 7x + 12


Putting x = (-3)


= (–3)2 + 7 (–3) + 12


= 9 + (-21) + 12


= 21-21


= 0


The error is (-21) instead of 4 and end result 0 instead of 25


Hence putting x = (-3) in x2 + 7x + 12 results to 0


More from this chapter

All 105 →
1

Find the errors and correct the following mathematical sentences

(2x)2 + 5x = 4x + 5x = 9x

1

Find the errors and correct the following mathematical sentences

(2a + 3)2 = 2a2 + 6a + 9

1

Find the errors and correct the following mathematical sentences

Substitute x = – 3 in


(b) x2– 5x + 6 = (–3)2 –5 (–3) + 6 = 9 – 15 + 6 = 0

1

Find the errors and correct the following mathematical sentences

Substitute x = – 3 in


(c) x2 + 5x = (–3)2 + 5 (–3) + 6 = – 9 – 15 = –24

Questions · 105
12. Factorisation
1 1 1 1 1 1 1 2 2 2 2 2 2 2 3 3 3 3 3 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 5 5 5 5 6 7 1 1 1 1 1 2 2 2 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
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