Answers − Substitution into Formulae

  1.   What is the value of 7 + 2a when a = 6?

	7 + 2a	= 7 + 2(6)
		= 7 + (2 × 6)
		= 7 + 12
		= 19

  2.   What is the value of 2x + 3 when x = 60?

	2x + 3	= 2(60) + 3
		= (2 × 60) + 3
		= 120 + 3
		= 123

  3.   What is the value of 35 + 4y when y = −5?

	35 + 4y	= 35 + 4(−5)
		= 35 + (4 × −5)
		= 35 − 20
		= 15

  4.   What is the value of 10 + 3a + b when a = 4 and b = −7?

	10 + 3a + b	= 10 + 3(4) + −7
		= 10 + (3 × 4) − 7
		= 10 + 12 − 7
		= 22 − 7
		= 15

  5.   What is the value of 2a + 3b + c when a = 2, b= 5 and c = −4?

  6.   What is the value of 4 + xy + z when x= −3, y = −7 and z = 6?

   note: − × − = +

  7.   What is the value of 9 + 2xyz when x = −6, y = −12, z = −3?

   note: − × − × − = −

  8.   What is the value of 2a + 3bc − 4c when a = −6, b = 7 and c = 8?

   note: + × − = −

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