Question

The value of a² if the expression (5x²+6x−7a) equals to 4 for x=2 is *
a. 16
b. 25
c. 17
d. 64

Answer 1

Answer:

5x^2+6x-7a=4 fr x=2

5(2)^2+6(2)-7a=4

5*4+12-7a=4

20+12-7a=4

32-7a=4

7a=32-4

7a=28

a=4

the value of a^2 is 4^2 i.e.16

so a is correct option

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Answer 2

$\sf \: (5 \times {2}^{2} + 6 \times 2 - 7 \times a) \: = \: 4 \\ \\ \sf \: (20 + 12 - 7a) \: = \: 4 \\ \\ \sf \: 32 - 7a \: = \: 4 \\ \\ \sf - 7a \: = \: 4 - 32 \\ \\ \sf \cancel- 7a \: = \: \cancel- 28 \\ \\ \sf a \: = \: \frac{28}{7} \\ \\ \color{lime} \sf \: a \: = \: 4$

$a^2\:=\:4\: \times \: 4\: =\:16$

$\sf Option\:a\:is\:the\:correct\: answer$