Dividing 2x2+13x+15 by x+5 and then substituting x=2 in the resulting expression gives
2x2+13x+15=2x2+10x+3x+15=2x(x+5)+3(x+5)=(2x+3)(x+5)(x+5)=2x+3
Substituting x=2 in resulting expression gives 2×2+3=7.
Find and correct the errors in the following mathematical statement. Substituting x = −3 in
(a) x2 + 5x + 4 gives (−3)2 + 5 (−3) + 4 = 9 + 2 + 4 = 15
(b) x2 − 5x + 4 gives (−3)2 − 5 (−3) + 4 = 9 − 15 + 4 = −2
(c) x2 + 5x gives (−3)2 + 5 (−3) = −9 − 15 = −24
Substituting x=−3 in x2+5x gives 32+5(−3)=−9−15=−24.