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Evaluate -1/2 x² + 3/4 x for x = 4.

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- -5

Solution:

1.Substitute

- Substitute x = 4 into $$\sf{ - \frac{1}{2} {x}^{2} + \frac{3}{4} \times }$$
- $$\sf{ - \frac{ {4}^{2} }{2} + 4 \times \frac{3}{4} }$$

2.Calculate

- $$\sf{ - \frac{16}{2} + 4 \times \frac{3}{4} }$$
- Cross out the common factor
- $$\sf{ - 8 + 4 \times \frac{3}{4} }$$
- Cross out common factor
- $$\sf{ - 8 + 3}$$
- Calculate the sum or difference
- -5

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